QALQILYA, West Bank – A policeman and three Hamas gunmen were killed Thursday when Palestinian forces loyal to President Mahmoud Abbas raided a West Bank house to arrest militants, the second such operation in the past week.

The raids, in the city of Qalqilya, appeared to be an effort by Abbas to show the United States that he was carrying out the Palestinian Authority's security commitments under a 2003 U.S.-backed peace road map.

A Hamas spokesman in the Gaza Strip said the operations had killed all chances for the success of the talks Egypt has been mediating between the Islamist group and Abbas's Fatah movement aimed at reconciling the rivals.

Adnan Damiri, spokesman for the security forces, said a gun battle erupted after police encircled a house in the city of Qalqilya where three Hamas gunmen were holed up. He said a policeman and the three gunmen were killed.

After the initial shooting died down, police prepared to storm the house, calling on the militants to surrender and throwing tear gas grenades inside.

Israel, which has demanded Abbas do more to rein in militants, has not met its road map obligations to halt the expansion of Jewish settlements in the occupied West Bank.

Six Palestinians -- two Hamas militants, three policemen and a bystander -- were killed in Qalqilya Sunday. Security officials said fighting erupted after the Hamas men refused to surrender to police.

Western-backed Abbas launched a U.S.-backed security drive in the West Bank and revived peace talks with Israel in 2007 after breaking with Hamas over the Islamist group's takeover of the Gaza Strip.

Hamas has threatened to pull out of the Cairo reconciliation talks, scheduled to resume in July, unless Abbas stops targeting its activists in the West Bank.

Fawzi Barhoum, a Hamas spokesman, said the West Bank raids were part of a plot ... to finish off resistance and the Hamas movement.

(Reporting by Mohammed Assadi, Naim Sweilem and Nidal al-Mughrabi; Writing Joseph Nasr; Editing by Ralph Boulton)