Dozens of troops and civilians were killed in a fresh round of border skirmishes between Pakistan and Afghanistan on Wednesday, officials on both sides of the frontier said, as clashes entered their second week.

Violence between the two neighbours has flared since explosions in Afghanistan last week, including two in the capital Kabul, that were blamed on Pakistan.

The Taliban government in Kabul launched an offensive along parts of its southern border in retaliation, prompting Islamabad to vow a strong response of its own.

Islamabad has accused Afghanistan of harbouring militant groups led by the Pakistani Taliban Tehreek-e-Taliban (TTP) on its soil, a claim Kabul denies.

In the latest violence, Pakistan's military accused the Afghan Taliban of attacking two major border posts in the southwest and northwest.

It said both assaults were repelled, with about 20 Taliban fighters killed in attacks launched near Spin Boldak on the Afghan side of the frontier in southern Kandahar province early on Wednesday.

"Unfortunately the attack was orchestrated through divided villages in the area, with no regard for the civil population," the military said in a statement.

It also said about 30 more were thought to have been killed in overnight clashes along Pakistan's northwest border.

The Afghan Taliban said 15 civilians were killed and dozens wounded in the clashes near Spin Boldak and that "two to three" of its fighters were also killed.

Ali Mohammad Haqmal, an Afghan spokesman for the information department in the Spin Boldak region, said civilians were killed by mortar fire.

Taliban government spokesman Zabihullah Mujahid accused Pakistani forces of "once again" carrying out attacks "with light and heavy weapons" in the district.

Mujahid said 100 civilians were also wounded, adding that calm had returned to the area after Pakistani soldiers were killed and posts and weapons seized.

The Pakistan military said these were "outrageous and blatant lies".

Pakistan did not give a toll for its losses in the latest clashes but said last week 23 of its troops had been killed in the opening skirmishes. (AFP)