Islamabad  - Taliban militants in Pakistan's north-western Swat valley extended their authority over another district after the government last week allowed Islamic sharia law to be imposed in the region, officials said Wednesday.

President Asif Ali Zardari approved a regulation on April 13 to impose Islamic sharia law in Malakand Division, which includes Swat and seven other districts, after a hardline cleric brokered a peace agreement between the regional government and the Taliban.

The accord is supported by the North West Frontier Province government, but has been criticized by liberal groups and Western nations because of fears that it would embolden the militants and expand their influence to other, calmer areas of the country.

"They [the militants] are fast gaining territory and have established checkpoints and dug bunkers at strategic locations in the mountains," said an official of the local administration in Buner district, about 100 kilometres north-west of Islamabad. Armed patrols have also begun, he added.

Several offices of governmental departments and charity organizations were ransacked and official vehicles driven away, the administrator told the German Press Agency dpa while requesting anonymity.

The insurgents also imposed a ban on playing music in vehicles, and were recruiting local residents to "join in implementing Islamic sharia."

Buner is part of Malakand, where authorities have yet to set up the new Islamic courts. The conservative population of Buner district reportedly accepted the imposition of sharia law with hopes for quick dispensation of justice, but they are said to be opposed to Taliban intrusion in their area.

A local tribal militia confronted Taliban militants earlier this month when they started infiltrating Buner, but the resistance subsided in following days in the face of relentless force and a reluctance on the part of government forces to stop the rebels.

Scenic Swat was one of Pakistan's most popular tourist resorts until 2007, when local radical cleric Maulana Fazlullah began an armed insurgency to enforce Taliban-style laws in the mountain district.

Sixteen months of pitched battles between Fazlullah's supporters and government forces killed hundreds of people and displaced nearly 300,000 more.

Relative calm returned following the February 16 peace deal, but the militants have so far refused to lay down their weapons as agreed with the government.

Prime Minister Yousuf Raza Gilani on Wednesday stressed that the pact was conditional, saying, "If peace is not restored, one can rethink and revisit [the agreement]."

Separately, rebels are believed to have kidnapped a government official along with two of his guards and a driver in Upper Dir district located adjacent to Swat.

Atifur Rehman was last seen in Chakdara village on Tuesday and went missing while driving back home late at night, a police official said on condition of anonymity. (dpa)