By Azaz Syed, Adam Pourahmadi, Helen Regan and Sophia Saifi, CNN

Islamabad, Pakistan (CNN) — Pakistan carried out a series of deadly military strikes on what it said were separatist militant hideouts inside Iran, in the latest incident across their shared border that has sent tensions between the two neighbors soaring.

The new strikes mean both Pakistan and Iran have now taken the extraordinary step of attacking militants on each other’s soil this week at a time of expanding conflict in the Middle East and wider region.

Islamabad said Thursday its forces launched a “series of highly coordinated and specifically targeted precision military strikes” in Iran’s southeastern Sistan and Baluchistan province as part of an operation called “Marg Bar Sarmachar” — a phrase which loosely translates to “death to the guerrilla fighters.”

It said the hideouts targeted in the operation were used by the Balochistan Liberation Army (BLA) and the Balochistan Liberation Front (BLF), two militant groups fighting for greater regional autonomy.

In a separate statement on Thursday, the BLF said it does not have any hideouts in Iran and that no BLF fighters had been killed in recent attacks. The BLA has not yet commented publicly on Pakistan’s strikes on Iranian territory.

A “number” of militants were killed during the operation, Pakistan’s Foreign Ministry added.

Tehran demanded “an immediate explanation” from Pakistan over the strikes, Iranian state-aligned Tasnim news agency reported, citing an official.

Meanwhile, Prime Minister Anwaar-ul-Haq Kakar, who is serving as caretaker leader until elections are held, cut short his visit to the World Economic Forum in Davos.

The caretaker Foreign Minister, Jalil Abbas Jilani, who is visiting Uganda, is also returning home.

Ten people were killed in the strikes, Tasnim news agency reported, citing the deputy governor of Sistan and Baluchstan, Alireza Marhamati.

“At 4:30 a.m. explosions were heard in a border village, several missiles were fired at the village,” Marhamati earlier said, according to Iranian state media IRNA.

The deputy governor said another explosion took place near the city of Saravan, but there were no casualties from that blast.

Both Pakistan and Iran have long fought militants in the restive Baloch region along their 900-kilometer (560-mile) border but the latest incident marks a major escalation between the two neighboring powers and comes as regional hostilities in the Middle East mount over Israel’s ongoing war in Gaza.

Pakistan on Thursday said it had expressed concern to Iran in recent years about the “safe havens and sanctuaries” of Pakistan separatist fighters, referred to as Sarmachar, living inside Iran, and that they had shared evidence of the presence and activities of the militants.

“However, because of lack of action on our serious concerns, these so-called Sarmachars continued to spill the blood of innocent Pakistanis with impunity. This morning’s action was taken in light of credible intelligence of impending large scale terrorist activities,” Pakistan’s Foreign Ministry said.

Pakistan said it “fully respects the sovereignty and territorial integrity of the Islamic Republic of Iran,” and that the “sole objective of today’s act was in pursuit of Pakistan’s own security and national interest which is paramount and cannot be compromised.”

Iranian strike on Pakistan

Pakistan’s operation comes a day after Iran said it used “precision missile and drone strikes,” to destroy two strongholds of the Sunni militant group Jaish al-Adl in Pakistan’s southwest Balochistan province, according to the Tasnim news agency.

The strikes killed two children and wounded several others, according to local officials and Pakistan’s Foreign Ministry, which described the attack as an “unprovoked violation of its airspace by Iran” and warned Iran of “serious consequences.”

It also kicked off a diplomatic spat with Pakistan on Wednesday recalling its ambassador from Iran and suspending all Iranian high-level visits.

A spokesperson for Pakistan’s Foreign Ministry said the Iranian Ambassador to Pakistan should not return from a current visit to Iran and warned “Pakistan reserves the right to respond to this illegal act.”

Iran has defended the strikes and appeared to seek to calm tensions with its nuclear-powered neighbor.

Iranian Foreign Minister Hossein Amir-Abdollahian said his country only targeted Iranian “terrorists” on Pakistan soil and that “none of the nationals of the friendly country of Pakistan were targeted by missiles and drones of Iran.”

An Iranian Foreign Ministry spokesperson earlier defended the strikes as a “precise and targeted” operation to deter security threats.

But the deadly attack inside Pakistani territory seriously damaged relations between the two countries, Foreign Minister Jilani told his Iranian counterpart.

“The Foreign Minister firmly underscored that the attack conducted by Iran inside Pakistani territory, on 16 January 2024, was not only a serious breach of Pakistan’s sovereignty but was also an egregious violation of international law and the spirit of bilateral relations between Pakistan and Iran,” the ministry said.

Jilani also warned that unilateral actions could undermine regional security, saying terrorism is a common threat that must be addressed through coordinated efforts, his office said.

Pakistan has also reiterated, however, that it considers Iran as “friends and brothers” and “have no interest in escalating any situation.”

The Baloch people live where Pakistan, Afghanistan and Iran meet. They have a history of exhibiting a fiercely independent streak and have always resented being ruled by both Islamabad and Tehran, with insurgencies bubbling across the porous border region for decades.

The area they live in is also rich in natural resources and Baloch separatists complain that their people, some of the region’s poorest, have seen little wealth trickle down to their communities.

Jaish al-Adl, or Army of Justice, targeted by Iran on Tuesday, is a separatist militant group that operates on both sides of the border and has previously claimed responsibility for attacks against Iranian targets.

Its stated goal is the independence of Iran’s Sistan and Baluchistan province, which neighbors Pakistan.

On Wednesday, it claimed responsibility for an attack on an Islamic Revolutionary Guard Corps (IRGC) vehicle in Sistan and Baluchistan that Iranian state media says killed one of its colonels.

Attacks by Iran and its allies

The strikes came after Iran’s Revolutionary Guards launched ballistic missiles, targeting what it claimed was a spy base for Israel’s intelligence agency Mossad in Erbil, northern Iraq, and at “anti-Iran terror groups” in Syria.

Iran said the strikes in Iraq were in response to what it said were Israeli attacks that killed Iranian Revolutionary Guard commanders, and claimed targets in Syria were involved in the recent dual bombings in the city of Kerman during a memorial for the slain Quds Force Commander Qasem Soleimani that left scores dead and wounded.

The international terror group ISIS has claimed responsibility for the attack on the Soleimani memorial.

Iran’s proxies in the region have also launched attacks on Israeli forces and its allies.

Houthi rebels have launched a series of attacks on commercial ships and Western military vessels in the Red Sea, a major artery for international trade. And Iranian-backed forces in Iraq and Syria have launched dozens of attacks aimed at US military positions in those countries.

Since Hamas’ October 7 attacks on Israel and the Israeli offensive in Gaza that followed, the militant group Hezbollah has engaged in daily confrontations with Israeli forces on the Lebanon-Israel border. On Wednesday, Israel’s military chief said the likelihood of war on the country’s northern border is now “much higher” than in recent times and Israel is increasing its readiness for “fighting in Lebanon.”

Iranian Foreign Minister Amir-Abdollahian told CNN at the World Economic Forum in Davos Wednesday that attacks by Iran-backed groups in the Middle East won’t stop until Israel’s war on Hamas in Gaza ends, as tensions across the region threaten to spiral into wider conflict.

This story has been updated with additional developments.