Afghanistan’s Taliban rulers said on Friday they were willing to negotiate after Pakistan bombed their forces in major cities and said the allies-turned-foes were in “open war.”

Pakistan struck the Afghan capital Kabul, the city of Kandahar, where Taliban leaders are based, and other towns, a Taliban spokesman said. The attacks were its first directly targeting Afghanistan’s government over allegations it harbours militants seeking to overthrow the Islamabad government.

Taliban spokesman Zabihullah Mujahid said there were civilian casualties on Friday but did not provide details.

In Kabul, thick plumes of black smoke rose from two sites and a huge blaze was also visible in video verified by Reuters. Reuters witnesses said many ambulance sirens could be heard following loud blasts and the sound of jets on Friday.

Kabul taxi driver Tamim said an ammunition depot was hit and explosions continued inside after the strikes as stored ordnance ignited.

“The plane came and dropped two bombs, then flew away again. After that, we heard explosions,” said Tamim, who was asleep when the strikes hit. “Everyone, in panic, ran down from the second floor of the house.”

Security sources in Pakistan said the strikes involved air-to-ground missile attacks on Taliban military offices and posts in response to Afghan attacks on Thursday.

The latest violence erupted after Pakistan’s airstrikes on Afghan territory last weekend triggered Afghan retaliatory attacks along the border on Thursday, escalating long simmering tensions over Pakistan’s claim that Afghanistan shelters Pakistani Taliban militants. Afghanistan denies this.

The Taliban said on Friday their leaders were ready to negotiate with Pakistan.

“The Islamic Emirate of Afghanistan has always tried to resolve issues through dialogue, and now also we want to resolve this matter through dialogue,” Mujahid said.

Mujahid said Pakistani strikes hit parts of Kabul, Kandahar and Paktia on Thursday night, and on Paktia, Paktika, Khost and Laghman on Friday.

That followed Afghan drone strikes that began late on Thursday on Pakistani military positions and installations in northwest Pakistan along their shared border.

Pakistani officials said the country’s strikes killed 274 Taliban officials and militants while Afghanistan said it killed 55 Pakistani soldiers - figures which Reuters was unable to verify.

Pakistan confirmed that 12 of its own soldiers were killed and Afghanistan said it had lost 13 Taliban fighters.

UN chief urges end to fighting, US expresses support for Pakistan

For years, Islamabad has blamed Afghanistan for attacks inside Pakistan aimed at overthrowing the government, claiming the Taliban shelter Tehreek e Taliban Pakistan fighters.

Islamabad says TTP leaders operate from Afghan territory and use it as a safe haven to plan cross border assaults. While the United Nations has said the TTP and the Taliban in Afghanistan are linked, the Kabul government denies this and argues Pakistan is deflecting blame for its own security failures.

In New York, UN Secretary-General Antonio Guterres was “deeply concerned by the escalation of violence” between Afghanistan and Pakistan and the impact that is having on civilian populations, his spokesperson Stephane Dujarric said.

“He calls for an immediate cessation of hostilities, and he reiterates his call on the parties to resolve any differences through diplomacy,” Dujarric said.

The United States on Friday expressed support for Pakistan.

“The United States supports Pakistan’s right to defend itself against attacks from the Taliban, a Specially Designated Global Terrorist group,” a State Department spokesperson said.

“The Taliban have consistently failed to uphold their counterterrorism commitments, allowing violence to destabilize the region while terrorist groups use Afghanistan as a launching pad for their heinous attacks.”

The European Union’s foreign policy chief Kaja Kallas on Saturday called for the countries to de-escalate and engage in dialogue.

“The EU reiterates that Afghan territory must not be used to threaten or attack other countries and calls on the Afghan de facto authorities to take effective action against all terrorist groups operating in or from Afghanistan,” Kallas said in a statement.

The strikes threatened to unleash a protracted conflict along the 2,600-km (1,615-mile) frontier between Afghanistan and Pakistan.

“Our cup of patience has overflowed. Now it is open war between us and you (Afghanistan),” Pakistani Defence Minister Khawaja Muhammad Asif said on Friday.

Pakistan’s foreign ministry warned that any new Taliban provocations, or attempts by any “terrorist group” to target Pakistanis, would be met with a “measured, decisive and befitting response”.

Pakistan is nuclear-armed and its military capabilities are vastly superior to those of Afghanistan. However, the Taliban are adept at guerrilla warfare, hardened by decades of fighting with US-led forces, before returning to power in 2021.

Afghan Foreign Minister Amir Khan Muttaqi spoke by telephone on Friday with Qatar’s Mohammed bin Abdulaziz Al-Khulaifi, the junior foreign minister, the Afghan ministry said in a statement.

Qatar, which helped stop fighting between the two countries last year, is working with other nations to help resolve the latest crisis, Afghanistan said.

“Afghanistan has never been a supporter of violence and has always preferred to resolve issues based on mutual understanding and respect,” Muttaqi told Khulaifi in their call, the statement said.

Clashes between Pakistan and Afghanistan in October killed dozens of soldiers until negotiations facilitated by Turkey, Qatar and Saudi Arabia brought an end to the hostilities.

The UN spokesman said nearly half of Afghanistan’s population, or 22 million people, need humanitarian aid and the number would rise if fighting continues or worsens.