KABUL/ISLAMABAD — Afghan and Pakistani forces traded air and artillery strikes into Sunday, with Kabul saying it fired on Pakistani jets over the capital and thwarted an attempted strike on Bagram, as fighting entered a fourth day along their 2,600-kilometer border.

Explosions echoed across parts of Kabul before dawn, followed by bursts of gunfire. Afghan authorities said Pakistani airpower attacked the capital at around 5:40 am local time, triggering a series of blasts and a response from Afghan air defense forces that lasted about 20 minutes.

Afghan government spokesman Zabihullah Mujahid said "anti-aircraft fire is being directed at Pakistani aircraft" and urged residents not to be concerned. Pakistan's prime minister's office and military did not immediately respond to requests for comment on the reported exchanges over Kabul.

North of the capital, residents said airstrikes hit the former US air base at Bagram. A provincial spokesman said Pakistani jets "attempted to bomb" the base, but there were no casualties or damage.

The latest escalation follows days of intensifying hostilities. Pakistan's military, backed by artillery and air power, has struck what it described as militant infrastructure and military installations inside Afghanistan. Islamabad said it was targeting the outlawed Tehreek-e-Taliban Pakistan, or TTP, which it accuses Kabul of sheltering — a charge the Afghan authorities deny.

Afghanistan has described the airstrikes as a violation of its sovereignty and said it launched retaliatory operations along the frontier. The defense ministry in Kabul said it carried out strikes on Pakistani military bases in Miranshah and Spin Wam overnight, destroying installations and causing heavy casualties.

Pakistan's Defense Minister Khawaja Muhammad Asif declared that "our patience has now run out. Now it is open war between us". Afghan Interior Minister Sirajuddin Haqqani warned the conflict would be "very costly".

Heavy losses

Casualty figures from both sides remain disputed and could not be independently verified. Pakistani officials said more than 330 Afghan forces had been killed and dozens of posts destroyed since fighting erupted. Afghan officials rejected the figures as inaccurate, saying their forces had inflicted heavy losses on Pakistani troops, while putting their own military deaths at 13.

Afghan authorities also accused Pakistan of targeting civilian areas in provinces, including Paktika, Khost, Kunar, Nangarhar and Kandahar, saying dozens of civilians, many of them women and children, had been killed since Thursday. Pakistan has said it is targeting only military installations.

Fighting has been reported at the Torkham border crossing, a key gateway for Afghans returning from Pakistan, with hundreds of residents fleeing the area.

Diplomatic efforts have intensified, with Saudi Arabia, Russia, China, the European Union and United Nations urging restraint and calling for talks.

Chinese Foreign Ministry spokeswoman Mao Ning said on Friday that China has been mediating and facilitating dialogue between Islamabad and Kabul through its own channel following fresh clashes along the Afghan-Pakistani border.

The escalation marks the most serious violence since October, when border clashes killed more than 70 people before a Qatari-mediated ceasefire. Although sporadic exchanges continued, the truce largely held until late February, when Pakistan struck what it said were TTP hideouts.

Agencies - Xinhua