ISLAMABAD (AP) — The Pakistani air force launched retaliatory strikes in Iran early Thursday, reportedly targeting militant hideouts. At least nine people were killed and tensions between neighboring countries continued to worsen.

The alleged attacks on Tuesday and Thursday appeared to target two Baloch militant groups with similar separatist goals on either side of the Iran-Pakistan border. However, the two countries accuse each other of providing safe haven for the groups in their respective territories.

The attacks threaten diplomatic ties between the two neighbors as Iran and nuclear-armed Pakistan have long viewed each other with suspicion over militant attacks. Each country also faces its own internal political pressures – and the strikes may be partly a response to that.

The attacks also come as the Middle East continues to be unsettled by Israel’s war with Hamas in the Gaza Strip. Iran also carried out airstrikes late Monday in Iraq and Syria over an alleged Islamic State (IS) suicide attack that killed over 90 people in early January.

Pakistan’s Foreign Ministry described their attack on Thursday as “a series of highly coordinated and targeted precision military strikes.”

“This morning’s actions were taken in light of credible intelligence of impending large-scale terrorist activity,” the State Department said in a statement. “This action reflects Pakistan’s unwavering resolve to protect and defend its national security from all threats.”

The Pakistani military described the use of “killer drones, missiles, loitering munitions and stand-off weapons” in the attack. Standoff weapons are missiles fired from aircraft from long distances – which likely means Pakistan’s warplanes have not entered Iranian airspace.

Pakistan’s Caretaker Prime Minister Anwaarul-Haq-Kakar, who is in Switzerland to attend the World Economic Forum in Davos, has cut short his trip and returned home.

A deputy governor of Iran’s Sistan and Balochistan province, Ali Reza Marhamati, gave the death toll from Thursday’s strike, saying the dead included three women, four children and two men near the border town of Saravan in Iran’s Sistan province and Balochistan. He added that the dead were not Iranian citizens.

The Baloch Liberation Army, an ethnic separatist group that has operated in the region since 2000, said in a statement that the attacks targeted and killed its people.

“Pakistan has martyred innocent Baloch people,” it said.

The Pakistani military also said the attacks hit targets linked to the Balochistan Liberation Front, although that group did not acknowledge the claim.

HalVash, an advocacy group for the Baloch people, posted images online that appeared to show the remains of ammunition used in the attack. It was said that several houses were attacked in Saravan. Videos were shared showing a building with mud walls being destroyed and smoke rising above the strike immediately afterwards.

Iran later summoned the Pakistani chargé d’affaires to the country. Pakistan had already withdrawn its ambassador due to Tuesday’s attack.

Pakistan named its operation “Marg Bar Sarmachar”. In Iranian Farsi, “marg bar” means “death to” – and has been a famous saying in Iran since the 1979 Islamic Revolution, referring to both the United States and Israel. In the local Baloch language, “Sarmachar” means guerrilla and is used by the militants operating in the border region.

Pakistan’s Balochistan province, as well as Iran’s neighboring Sistan and Balochistan provinces, have faced low-level insurgencies by Baloch nationalists for more than two decades.

However, the target groups of the strike days are different. Jaish al-Adl, the Sunni separatist group that Iran targeted on Tuesday, grew out of another Islamist extremist group called Jundallah that once had alleged ties to al-Qaeda. Jaish al-Adl has long been suspected of operating from Pakistan and carrying out attacks on Iranian security forces.

The Baloch Liberation Army, which has no religious component and has carried out attacks against Pakistani security forces and Chinese interests, is suspected of hiding in Iran. The Balochistan Liberation Front is similarly nationalistic.

Both Iran and Pakistan are under domestic political pressure. Iran is under increasing pressure to act following the attack by the Islamic State terrorist militia, Israel’s war against Hamas and major unrest against its theocracy. Meanwhile, Pakistan faces crucial parliamentary elections in February as the military remains a strong force in the country’s politics.

The risk of escalation remained on Thursday as the Iranian military is set to launch a planned annual air defense exercise from its Chabahar port near Pakistan through the entire south of the country and into Iraq. Exercise Velayat 1402 involves live fire from aircraft, drones and air defense systems.

Iran and Pakistan share a 900-kilometer (560-mile) largely lawless border that allows smugglers and militants to travel freely between the two nations. The route is also crucial for the global transport of opium from Afghanistan. The Taliban separately urged restraint in view of the tensions.

For both Iran and Pakistan, the cross-border attacks again raise questions about the readiness of their own forces, particularly their radar and air defense systems.

Such systems are crucial for Pakistan as tensions with India, its nuclear-armed rival, remain consistently low. Their equipment has long been stationed at the border and not on the border with Iran. Iran relies on these systems to deter possible attacks from its main enemy, the United States

“The government and military were under enormous pressure,” said Abdullah Khan, an analyst at the Pakistan Institute for Conflict and Security Studies. “Iran celebrated the attack (on Tuesday) in its media and Pakistan’s public perception of a strong army is not what it used to be, so it had to respond.”

Complex geopolitical considerations also play a role in the tensions. Pakistan’s military relies on American, Chinese and French fighter jets for its air force – meaning some of those foreign weapons were used in Thursday’s attack.

China, an important partner for both countries, urged restraint. Beijing is a major regional player and has developed a major Belt and Road project at Gwadar port in Pakistan’s Balochistan province. Baloch, the Foreign Ministry spokeswoman, said she was not aware of any direct Chinese mediation in the conflict, although Beijing had offered it.

“China sincerely hopes that both sides can exercise calm and restraint and prevent tensions from escalating,” Chinese Foreign Ministry spokesman Mao Ning said on Thursday.

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Gambrell reported from Jerusalem. Associated Press writers Riazat Butt in Islamabad and Nasser Karimi in Tehran, Iran, and video producer Liu Zheng in Beijing contributed to this report.