A Palestinian has died in confrontations with Israeli forces who are searching for three teenagers believed to have been kidnapped, witnesses and hospital officials said this morning.

Israeli forces swept into a second West Bank city today and the bloodshed near Ramallah marked an escalation in the situation.

Witnesses said Palestinians threw rocks at soldiers conducting house-to-house searches in al-Jilazoun refugee camp, outside Ramallah, before dawn.

Army gunfire killed a 20-year-old Palestinian and wounded another, hospital officials said.

The military had announced plans to step up its West Bank operations to locate the three Israeli teens who disappeared after leaving a Jewish settlement on Thursday.

It did not immediately comment on the al-Jilazoun incident.

Over the weekend troops rounded up scores of Palestinians in Hebron, a West Bank city where support for the Islamist faction is strong.

Among the detainees were several Palestinian politicians from Hamas, including parliament speaker Aziz Dweik, witnesses said.

The crisis is a double test for President Mahmoud Abbas. His security forces have sought to help Israel's search, drawing censure from Hamas.

Israeli Prime Minister Benjamin Netanyahu blamed Hamas for abducting the three teenagers and holds Mr Abbas responsible for their return.

Hamas has neither confirmed nor denied Israel's allegation.

Over the weekend, several rockets were fired into Israel from Gaza, a Palestinian territory under Hamas control.

Israel launched air strikes at Gaza training camps used by Hamas and Islamic Jihad, another Palestinian militant group.

There were no serious casualties on either side.