The so-called People's Peace Movement attracted international attention last year when they walked across Afghanistan and into the capital Kabul in an attempt to reduce the record levels of violence across the country.

Thousands of civilians have been killed or injured in the past 18 years of fighting between the militant group and US-backed forces.

About 30 members of the People's Peace Movement started a new walk on May 27, when they set out from Lashkar Gah, capital of Helmand province.

According to Abdul Malik Hamdard, a peace march supporter, the Taliban forced four members of the group to accompany them in vehicles Sunday night as they crossed into Taliban territory in the south of the country.

Then on Monday, Taliban fighters returned and took the rest of the group, except for a few older members, he added. About 25 marchers were detained in total, he said.

"Initially (the Taliban) told us that 'we will talk to them'," Hamdard told AFP.

"We have had no news from them since then."

After refusing to comment about the marchers' plight for more than 36 hours, the Taliban on Tuesday released photos of four of the group including its leader, Iqbal Khyber, and said the men were safe and would not be harmed.

"We do not know for what purpose the Taliban fighters have taken our members," another supporter, Bacha Khan Muladad, told AFP.

"We don't know whether they have been taken hostages or are negotiating with them."

Muladad added he had been unable to contact any of the members directly because their phones were switched off.

Bismillah Watandost, the marchers' spokesman who is now among the detained group, last week told AFP that the group aims to express to the Taliban the pain and suffering of Afghans, and call for a ceasefire over the festival of Eid, which began Tuesday.

The group had initially planned to march to Mosa Qala, a Taliban's stronghold some 130 kilometres (80 miles) from Lashkar Gah.

According to the UN, almost 4,000 civilians -- including more than 900 children -- were killed in Afghanistan last year, with more than 7,000 wounded. It was the deadliest year on record.

After 18 years of conflict, the Taliban are in negotiations with the US for some sort of peace settlement. But a resolution still seems far off, with the two sides struggling to agree on several key points.