At least one Afghan civilian and two Pakistani security forces were killed in the clash, said Abdul Hanan Zadran, acting police chief for Afghanistan's eastern province of Khost.

The bodies of the two Pakistanis were found on the Afghan side of the border near Pakistan's tribal belt, Zadran told AFP. Three civilians were also wounded, he added.

Khost provincial governor spokesman Talib Mangal confirmed the incident, but said two Afghan civilians and four Pakistani troops were killed.

Two Pakistani security forces were also detained on Afghan soil, he added.

Afghan officials often give conflicting casualty figures.

The Pakistani military said two members of its paramilitary Frontier Corps were "carrying out routine surveillance" along the border when they were "fired upon from Afghanistan".

Two of them died and five others were wounded, it said in a statement, without confirming if the Pakistani security forces also opened fire.

"Pakistani troops are exercising maximum restraint so as to avoid any Afghan civilian casualties. Military engagement is under way to defuse situation," read the statement.

Earlier this month, Afghanistan accused Pakistan of carrying out air strikes in its Kunar province, causing "massive property damage" -- charges Islamabad vehemently denied.

Kabul has long-accused Islamabad of providing safe havens for the Afghan Taliban, which has been waging an insurgency in Afghanistan for more than 16 years.

Islamabad rejects the accusation, countering that Islamist militants targeting Pakistani forces and civilians reside on the Afghan side of the border.

The issue of alleged safe havens remain a major source of tension between the two countries.

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