Pakistan’s president Saturday warned neighboring Afghanistan’s Taliban government that it had “ crossed a red line ” by launching drone attacks on civilian areas in Pakistan, and hours later the country reportedly conducted strikes on an Afghan drone storage facility.

The statement by Asif Ali Zardari was the latest in what has become the deadliest fighting yet between the two South Asian neighbors. The cross-border clashes, which erupted late last month, have shown no signs of abating despite efforts by China and Turkey to broker a ceasefire.

Pakistan said its forces intercepted the drones launched Friday but that falling debris injured two children in the city of Quetta and two people elsewhere in the country.

According to state-run media, Pakistan’s air force carried out strikes late Saturday in Afghanistan’s southern Kandahar Province, targeting an Afghan military facility that had allegedly been used to launch drone attacks into Pakistan a day earlier and that the facility was also being used by the Pakistani and Afghan Taliban for “acts of terrorism” in Pakistan. Pakistan TV, citing security officials, reported that the latest strikes were intended to signal to Kabul that Afghan territory cannot be used for cross-border attacks against Pakistan.

On Friday, the Afghan Taliban government accused Pakistan of conducting airstrikes in Kabul, the country’s capital, and other areas in eastern Afghanistan, saying at least six civilians were killed and 15 other were injured.

Hours later, Kabul claimed its air force responded by targeting military installations near Islamabad, Pakistan’s capital, and in northwestern Pakistan.

Pakistan denied targeting civilians, saying its operations are focused on Pakistani Taliban militants and their support networks. Islamabad has referred to the conflict as an “open war” — adding to concerns among the international community about regional stability as the U.S.-Israeli war with Iran has engulfed the Middle East and beyond.