Afghanistan accused Pakistan of killing at least 400 people in an airstrike on a drug rehabilitation hospital in Kabul late Monday, marking a dramatic escalation in cross-border clashes that have intensified over the past three weeks.

The Afghan government stated the strike hit the 2,000-bed facility around 9 p.m. local time, destroying large sections and causing a death toll that had “so far” reached 400 people, with approximately 250 injured. Local television footage showed security forces using flashlights to carry casualties from the ruins while firefighters battled flames.

Zabihullah Mujahid, a Taliban spokesperson, condemned the attack on social media, accusing Pakistan of “targeting hospitals and civilian sites to perpetrate horrors” and calling it “a crime against humanity.” Pakistan swiftly denied the allegations.

“No hospital was targeted in Kabul,” said Mosharraf Zaidi, spokesperson for Pakistani Prime Minister Shehbaz Sharif. Information Minister Attaullah Tarar said Pakistani forces conducted “precision airstrikes” targeting military installations in Kabul and Nangarhar province, destroying “technical support infrastructure and ammunition storage facilities” used by the Afghan Taliban regime to support terror proxies.

The strike occurred hours after Afghan and Pakistani forces exchanged fire along their border, killing four people in Afghanistan, according to Afghan officials. The deadliest fighting between the neighbors in years has now entered its third week.

The United Nations Security Council on Monday called on Afghanistan’s Taliban rulers to immediately step up efforts to combat terrorism, extending the UN political mission in Afghanistan for three months. The resolution did not specifically mention Pakistan’s attacks but condemned “in the strongest terms all terrorist activity including terrorist attacks.”

Pakistan accuses Afghanistan of harboring militant groups, particularly the Pakistani Taliban, which is designated as a terrorist organization by the United States, as well as Baloch separatist groups that target Pakistani security forces and civilians. Kabul denies providing safe haven.

The conflict began in late February after Afghanistan launched cross-border attacks in response to Pakistani airstrikes inside Afghanistan that Kabul said killed civilians. The clashes disrupted a ceasefire brokered by Qatar in October after earlier fighting killed dozens of soldiers, civilians, and suspected militants.

Pakistan has declared it is in “open war” with Afghanistan, a stance that has alarmed the international community due to the presence of other militant organizations, including al-Qaida and the Islamic State group, in the region.

Pakistani President Asif Ali Zardari said Afghanistan’s Taliban administration crossed a “red line” by deploying drones that injured several civilians in Pakistan last week. In response, Pakistan’s air force struck equipment storage sites and “technical support infrastructure” in Afghanistan’s southern Kandahar Province over the weekend, which Kabul said included an empty security site and a drug rehabilitation center that sustained minor damage.

In Kabul, Abdul Salam Hanafi, Afghanistan’s administrative deputy prime minister, said defending sovereignty is the duty of all citizens. Speaking during a meeting with political analysts and media figures, Hanafi expressed regret over civilian casualties in recent Pakistani attacks, stating the war was imposed on Afghanistan.