Watch Paul Adams's report on the demonstrations

The worst trouble was at El Bireh - the home town of Imad and Adel Awadallah who were shot dead on Friday.

Israeli troops fired rubber bullets at Palestinian protesters who had marched from nearby Ramallah.

The protesters chanted anti-Israeli slogans and calls for revenge.

There are conflicting reports of the number of casualties, but it could be around 100.

There were also protests in the towns of Nablus and Hebron, and elsewhere in the West Bank.

'Planning attacks

Israel said that it was tipped off three days ago that two major Hamas figures were hiding out in a summer cottage west of Hebron.

The Israeli army said the Awadallah brothers apparently had planned to kidnap Israelis or carry out a drive-by shooting.

Israel says weapons were found at the hideout

An army spokesman said a large number of weapons were found in the house where the brothers were killed.

Following the shootings, the Israeli army sealed off the West Bank and Gaza Strip to prevent Palestinians from entering Israel.

Israeli security forces were also put on alert following statements from Hamas leaders vowing revenge.

The rise in tension coincides with a visit to the Middle East by the US special envoy Dennis Ross.