QUSRA, West Bank, Sept 5 (Reuters) - Jewish settlers set fire to part of a mosque in the occupied West Bank on Monday, Palestinians said, an attack that looked like a reprisal for Israel's dismantling of three buildings in an unauthorized settlement outpost hours earlier.

Abdel Azeem Wadi, a member of the village council in Qusra near the Palestinian city of Nablus, said settlers threw burning tires into the mosque, damaging the entire first floor.

Earlier on Monday, Israeli authorities following a court order demolished three houses in Migron, a hilltop outpost.

The names of Migron and a second Jewish outpost were written in Hebrew on the mosque walls. Police said they were investigating the attack.

Some settlers have threatened to exact a price on Palestinians in response to Israeli government actions against settlements.

Six people who scuffled with police were arrested in Migron, a police spokesman said.

Migron is one of about 100 small outposts that settlers built without government approval on land that Israel captured in a 1967 war and which Palestinians want for a future state.

Settler-related incidents resulting in Palestinian injuries and damage to property are up more than 50 percent this year, according to the U.N. Office for the Coordination of Humanitarian Affairs, which documents violence in the Palestinian territories. (Reporting by Abed Omar Qusini, Tom Perry and Ari Rabinovitch; Editing by Mark Heinrich)