At least 400 people were killed and 250 injured in an air strike by Pakistan on a drug rehabilitation hospital in ​Kabul, a spokesman of the Afghan Taliban government said on Tuesday, a sharp escalation in the conflict between the neighbours.

Pakistan rejected the claim as false and misleading and said it "precisely ‌targeted military installations and terrorist support infrastructure" on Monday night.

"The visible secondary detonations after the strikes clearly indicate the presence of large ammunition depots," Pakistani Information Minister Attaullah Tarar said in a post on X.

The air strike came hours after China said it remained ready to continue efforts to ease tensions between the South Asian Islamic nations and urged both to avoid expanding the war and return to the negotiating table.

The conflict that began last month is the worst ever between the neighbours who share ​a 2,600-km (1,600-mile) border. It had ebbed amid attempts by friendly countries, including China, to mediate and end the fighting before flaring up again, this time just days before the Eid al-Fitr festival that marks ​the end of the holy month of Ramadan.

The escalation comes amid wider instability in the neighbourhood where the US-Israeli strikes on Iran and Tehran's retaliation have plunged ⁠the Middle East into a crisis.

It was like Doomsday, says a Survivor

At the site, a blackened single-storey structure bore the marks of flames. In other places, buildings were reduced to heaps of wood and metal, ​with only a few bunk beds still intact in some, while blankets, personal belongings and bedding were strewn about.

Witnesses said they heard three bombs exploding just as people in the hospital were completing evening prayers and two ​of them struck rooms and patient areas.

"The whole place caught fire. It was like doomsday," said Ahmad, 50, who said he was under treatment at the facility and gave only his first name. "My friends were burning in the fire, and we could not save them all."

Visuals from local media taken overnight showed flames engulfing a single-storey building, while thick smoke billowed from another section of the same complex and workers took away bodies on stretchers.

Ambulances and police vehicles were parked near the gate ​of the damaged facility, which a sign identified as a "drug addiction treatment hospital" with 1,000 beds, while security personnel maintained guard.

"When I arrived (last night), I saw that everything was burning, people were burning," ambulance driver Haji ​Fahim told Reuters. "Early in the morning they called me again and told me to come back because there are still bodies under the rubble."

'Constant lies' says Pakistan

Hamdullah Fitrat, the deputy spokesman for the Taliban, said the air strike took ‌place at 9 ⁠p.m. (1630 GMT) on Monday and targeted the state-run Omid hospital, which he said was a 2,000-bed drug rehabilitation centre.

"Large parts of the hospital have been destroyed, and there are fears of heavy casualties," he said in a post on X. "Sadly, the number of those killed has so far reached 400, with up to 250 others injured."

Rescue teams were at the scene working to control the fire and recover the victims, he added, without sharing details of how many bodies had been recovered and how the casualties had been counted.

Reuters could not verify the casualty numbers. Through the conflict, both sides have claimed to have inflicted heavy damage on the other but independent verification ​has not been possible.

The spokesman for Pakistan's prime minister ​called the Afghan reference to drug users being ⁠targeted as "constant lies" and said Pakistan's "counter-terrorism operations" would continue for as long as it took to eliminate "terrorists and their infrastructure".

Overnight, the Pakistani Information and Broadcasting Ministry said the Afghan Taliban claim was "misreporting of facts".

"Pakistan's targeting is precise and carefully undertaken to ensure no collateral damage is inflicted," it said in a post on X. "This misreporting ​of facts as drug rehabilitation facility seeks to stir sentiments, covering illegitimate support to cross-border terrorism."

The Omid hospital was established in 2016 and has treated hundreds ​of people, also providing them ⁠with vocational training such as tailoring and carpentry to make them more employable, according to local media reports.

Fierce fighting between the South Asian neighbours, who were close allies earlier, erupted last month with Pakistani air strikes in Afghanistan that Islamabad said targeted militant strongholds.

Afghanistan called the strikes a violation of its sovereignty that targeted civilians and launched its own attacks.

Islamabad says Kabul provides a safe haven to militants launching attacks on Pakistan. The Taliban deny the allegation, ⁠saying tackling militancy ​is Pakistan's internal problem.

Richard Bennett, the UN Special Rapporteur for human rights in Afghanistan, said he was "dismayed" by fresh reports of ​Pakistani air strikes and resulting civilian deaths.

"My condolences. I urge parties to de-escalate, exercise maximum restraint and respect international law, including the protection of civilians and civilian objects such as hospitals," he said in a post on X.