As with previous rounds of hostilities between Pakistani and Afghan forces, each side has accused the other of attacking first – and both claim to have inflicted heavy losses on the other side.

Pakistan’s Prime Minister Shehbaz Sharif said his country’s forces were able to “crush” its foes, while its defence minister had declared “open war” on the Taliban in Afghanistan.

The Afghan Taliban “will retaliate if we are attacked, but we won’t start clashes at the moment”, a Taliban military spokesperson told the BBC.

The group’s chief spokesman Zabihullah Mujahid said the offensive had killed “numerous” Pakistani soldiers and captured others – a claim denied by Pakistani authorities.

Mosharraf Zaidi, spokesman for Pakistan’s prime minister, said 133 Afghan Taliban fighters had been killed and more than 200 wounded by Pakistani forces as of 22:50 GMT on Thursday. Again, the BBC has not been able to verify these figures.

UN officials have called for an immediate de-escalation of the fighting, while Iran, which shares borders with both nations, has offered to mediate.

Iranian Foreign Minister Abbas Araqchi noted it was currently Ramadan, “the month of self-restraint and strengthening of solidarity in the Islamic world”.

China, which counts itself as friendly to both Afghanistan and Pakistan, called for a ceasefire, with foreign ministry spokeswoman Mao Ning urging them to “remain calm and exercise restraint”.

The foreign minister of Pakistan’s ally Saudi Arabia met his Pakistani counterpart to discuss ways to reduce tensions.

The air strikes follow months of hostilities between the two countries. The last serious flare-up was in October, after which a fragile ceasefire brokered by Turkey and Qatar was reached.

Pakistan accuses Afghanistan’s Taliban government of supporting “anti-Pakistan terrorists” who it blames for carrying out suicide attacks in Pakistan, including a recent one at a mosque in Islamabad.

This is a claim disputed by the Taliban government, which has repeatedly said the territory of Afghanistan is not being used to threaten the security of other countries.

It, in turn, accuses Pakistan of carrying out unprovoked attacks in which civilians have been killed. Pakistan says it only targets militants.

Earlier this week, Pakistan carried out multiple overnight air strikes on Afghanistan, which the Taliban has said killed at least 18 people, including women and children.

Outgunned by nuclear-armed Pakistan, analysts believe that it is unlikely for the Taliban to fight a conventional war with Pakistan. However, the Afghan Taliban has extensive experience in guerrilla warfare.

What makes the latest round of Pakistani strikes significant is that they have targeted Taliban government facilities instead of terrorist targets in Afghanistan, Michael Kugelman, a senior fellow for South Asia at the Atlantic Council, told the BBC’s Newsday programme.

“It’s now targeting the regime itself,” he said.

Meanwhile, rhetoric from the Taliban suggests it is committed to “staging relentless attacks” on Pakistan – a “precarious situation” that could lead to an actual conflict.

The Afghan Taliban’s military chief, Qari Muhammad Fasihuddin, said in a video message on Friday that Pakistan could expect “an even more decisive response” in future.

Additional reporting by the BBC Afghan and Urdu teams