KABUL (REUTERS) - Afghanistan's Taleban demanded the release of political prisoners among a list of conditions that they said on Sunday would need to be met before they consider rejoining peace talks aimed at ending the 15-year war.

Taleban forces have stepped up their campaign in the last year to topple the Kabul government, which has struggled since most of the foreign troops left at the end of 2014.

The Islamist insurgents are demanding the release of an unnamed list of prisoners, to be removed from a UN blacklist freezing their assets and imposing a travel ban on its leaders, and to have a political office formally recognised.

These are "among the preliminary steps needed for peace",the Taleban said in a statement. "Without them, progress towards peace is not feasible."

The demands came a day after representatives of the Taleban and former Afghan officials met in Qatar at a conference to resolve the war organised by the Pugwash Conferences on Science and World Affairs, a Nobel peace prize-winning crisis group.

The rare talks are a step toward a peace process that has proved elusive during a 15-year war that has killed tens of thousands of Afghans since the Taleban were driven from power by a 2001 US-led military operation.

Afghanistan, Pakistan, China and the United States met last week to lay the ground for a negotiated end to the war and called for the Taleban to rejoin the peace process.

The first formal peace talks with the Taleban since the start of the war collapsed last year after it was announced that founder Mullah Mohammad Omar, who sanctioned the talks, had been dead for two years, throwing the group into disarray.

Despite the efforts to restart talks, the Taleban since the start of the year have ramped up their campaign of violence across Afghanistan, with suicide attacks and territorial gains in Helmand province.