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Afghan Taliban forces killed six civilians in Pakistan and injured at least 17 others in an "unprovoked" bombing and gunfire attack on a border town on Sunday, Pakistan says.

The attack at Chaman was condemned by Pakistan's military who said the Afghan side launched "indiscriminate fire".

Pakistan forces retaliated. One Afghan soldier was killed.

It's unclear exactly what sparked the clash at the crossing over the border, which the two sides dispute.

However, it comes amid a rise in tensions between the neighbouring countries over security issues, since the Taliban regained control of Afghanistan last year.

Pakistan's Prime Minister Shehbaz Sharif said the Afghanistan action "deserve[d] the strongest condemnation".

The border dividing the two nations was drawn arbitrarily by the British in 1893 and is called the Durand Line. It is disputed by Afghanistan and millions of ethnic Pashtuns living on either side of it.

Afghan security sources, cited by Reuters news agency, said the incident happened after Pakistan demanded Afghan border forces stop building a checkpost on their side of the border.

Meanwhile AFP news agency quoted anonymous Afghan government officials saying tensions flared up after Afghan forces tried to cut part of a fence on the border.

Since 2017, Pakistan has been building a massive fence along the border - something objected to by both the Taliban, who took power last year, and the previous Afghan government.

Pictures from the border town on Sunday showed people wounded by artillery shelling and the fiery remains of hit vehicles and damaged roads.

"A mortar shell landed and caused a huge fireball. After that, I lost consciousness and don't know what happened," one hospitalised victim told Al Jazeera news organisation.

The Kandahar governor confirmed a Taliban member had been killed and 10 people were wounded.

The crossing was closed after the shooting, but authorities said it re-opened later later on Sunday after representatives from both sides met.

There have been previous clashes along the Chaman crossing - one of the major transit checkpoints between Afghanistan and Pakistan and used by thousands of people each day. Last month, it was closed for eight days after a gunman shot dead a Pakistan security guard.

Pakistani officials say attacks launched by Pakistani militant groups from Afghan territory have become more frequent since the Taliban took power.

They have also accused the new Taliban government of sheltering those groups in Afghanistan. The Taliban deny this.

Pakistan's embassy in Kabul, the Afghan capital, was attacked by gunmen two weeks ago, in what Islamabad described as an assassination attempt on their head diplomat.