Tribal groups in the Pakistani region of North Waziristan say they have taken control of the main town of Miranshah to maintain law and order.
Notices posted on the city's walls asked locals to report any suspicious people or activities to them.
A tribal elder told the BBC that this was part of a peace deal agreed with Pakistan's government and pro-Taleban tribal leaders earlier this month.
He said this was done to stop kidnappings, killings and thefts.
Around 80 armed men, among them members of militant groups, have been posted across the town. There has been no comment from the government.
North Waziristan lies near the border with Afghanistan.
The agreement calls for local tribesmen to stop sheltering Taleban and al-Qaeda fugitives and prevent them from crossing the border into Afghanistan.