JERUSALEM?A top Palestinian militia leader and two of his fighters were killed Thursday in the West Bank by an explosion their colleagues blamed on Israel. The blast came only hours after Prime Minister Ariel Sharon threatened retaliation for the assassination of an Israeli Cabinet minister.

Elsewhere in the West Bank, Israeli tanks seized outlying neighborhoods of two Palestinian towns. The incursions triggered gun battles, and doctors said three Palestinians were killed, including a 12-year-old girl hit by Israeli fire at her school.

The burst of violence threatened Washington?s efforts to retain Arab and Muslim support for U.S. military action against Islamic militants suspected of having masterminded the Sept. 11 terror attacks on New York and Washington. The United States is courting moderate Arab states and fears Israel Palestinian violence could interfere.