Afghanistan has said it was firing at Pakistani jets in Kabul after blasts and gunfire rocked the capital, compounding instability in a region rattled by US-Israeli strikes on Iran and retaliatory attacks on US targets in Gulf states.
The Taliban-ruled state has suffered Pakistani strikes against government installations over the past week following accusations, which it denies, that it harbours militants.
The heaviest fighting in years between the neighbours has raised fears of a protracted conflict along their 2,600km border, with several countries including Qatar and Saudi Arabia calling for restraint and offering to help mediate a ceasefire.
Explosions echoed across parts of Kabul before sunrise, followed by bursts of gunfire, a witness said.
It was not clear what had been targeted or whether there were casualties.
Taliban administration spokesperson Zabihullah Mujahid said the sounds were the result of Afghan forces targeting Pakistani aircraft over the capital.
"Air defence attacks were carried out in Kabul against Pakistani aircraft. Kabul residents should not be concerned," Mr Mujahid said.
Pakistan's prime minister's office, information ministry and military did not respond to requests for comment.
The violence follows air strikes inside Afghanistan this week that Pakistan said targeted militant infrastructure.
Afghanistan described the strikes as a violation of sovereignty and announced retaliatory operations along their shared border.
Iran, which shares borders with both Afghanistan and Pakistan, had offered to help facilitate dialogue before itself coming under attack yesterday from Israel and the US bent on diminishing Iran's military capability.
Pakistan has said Afghanistan harbours Tehreek-e-Taliban Pakistan (TTP) militants, which it said are waging an insurgency inside Pakistan.
Afghanistan has denied the accusation, saying it does not allow Afghan territory to be used against other countries and that Pakistan's security challenges are an internal matter.
Pakistani security sources have said operation "Ghazab Lil Haq", meaning "Wrath for the Truth", was ongoing and that Pakistani forces had destroyed Afghan posts and camps.
Both sides have reported heavy losses, issuing differing casualty figures for each other.
Diplomatic efforts have intensified, with Saudi Arabia, Russia, China, the European Union and United Nations urging restraint and calling for talks.
The US said it supports Pakistan's right to defend itself.
Pakistan Defence Minister Khawaja Muhammad Asif described the fighting as "open war".
Afghanistan Interior Minister Sirajuddin Haqqani said the conflict would be "very costly". He said only front-line forces were engaged in fighting that the country has yet to fully deploy its military.
