Afghan troops clashed with Pakistani forces near the disputed border on Sunday, in fighting that killed two Pakistani paramilitaries and wounded five others, officials said.
Pakistan's military said in a statement that the Frontier Corps was carrying out "routine surveillance" along the border when it was "fired upon from the Afghanistan side." It said the paramilitaries showed "maximum restraint" to avoid civilian casualties, and that "military engagement" is underway to defuse the situation.
Col. Abdul Hanan, interim chief of the Afghan National Police, said clashes broke out in the morning when Pakistani border forces allegedly opened fire at Afghan villages in Zazi Maiden district along the Durand Line.
According to Hanan, two Pakistani guards were arrested.
The two countries are separated by the 2,400-kilometer (1,500-mile) Durand Line, which was drawn by British rulers in 1896. Afghanistan does not recognize it as an international border and has objected to new fortifications being built by Pakistan.
The two U.S. allies routinely accuse each other of failing to crack down on militants who operate along the porous border. Khost province lies next to the restive tribal belt in Pakistan.