By Sahibzada Bahauddin

KHAR, Pakistan, Aug 15 (Reuters) - About 100,000 Pakistani villagers have fled clashes between security forces and militants in a northwestern region raising the danger of a big humanitarian problem, a government official said on Friday.

Security forces and militants have been fighting in the Bajaur region on the Afghan border, a known sanctuary for al Qaeda and Taliban fighters, since the militants attacked a security post last week.

About 170 people have been killed, including some civilians, officials have said. The fighting has included strikes on militants by fighter jets and helicopter gunships.

The violence has triggered an exodus, with people streaming out of the region on packed pick-up trucks and on foot, many heading for the safety of the main northwestern city of Peshawar.

The displaced people are creating one more problem for a new coalition government pre-occupied with political wrangling while economic and security problems mount.

"We are gathering figures from various areas and it is close to 100,000, it may be more than that," said Sitara Imran, Minister for Social Welfare in the North West Frontier Province.

"This will create a big humanitarian problem ... We are going to appeal to civil society and international donor agencies for help," Imran said.

Bajaur is the most northerly of seven semi-autonomous tribal regions. It is opposite Afghanistan's eastern province of Kunar, where U.S. troops are battling al Qaeda and Taliban fighters.

Villager Mohammad Maroof walked for many hours with his family to get out of Bajaur, where he said life had become intolerable.

"There is no such thing as life in Bajaur. We were like a prisoners in our own homes," said Maroof, who has taken refuge with friends in Peshawar.

Imran said the humanitarian situation was expected to deteriorate with people also leaving the northwestern valley of Swat where troops are also battling militants.

Nearly 150 people have been killed in two weeks of renewed clashes in the valley, which until last year was one of the country's main tourist destinations.

The election of a civilian government in February brought a lull in militant violence as new leaders sought to make peace deals in various trouble spots but trouble has flared again in recent weeks. (Additional reporting and writing by Augustine Anthony; Editing by Robert Birsel and David Fox)

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