The Taliban have stepped up their search for people who worked for Nato forces or the previous Afghan government, a UN document has warned.

It said the militants have been going door-to-door to find targets and threaten their family members.

The hardline Islamist group has tried to reassure Afghans since seizing power in a lightning offensive, promising there would be "no revenge".

But there are growing fears of a gap between what they say and what they do.

The warning the group were targeting "collaborators" came in a confidential document by the RHIPTO Norwegian Center for Global Analyses, which provides intelligence to the UN.

"There are a high number of individuals that are currently being targeted by the Taliban and the threat is crystal clear," Christian Nellemann, who heads the group behind the report, told the BBC.