Dozens of Palestinian youths clashed with Israeli soldiers in the occupied West Bank city of Bethlehem last night as Israel continued a four-day offensive against Hamas in Gaza.

At the entrance of Bethlehem, a frequent flashpoint of violence, youths threw stones at Israeli soldiers, who fired back with tear gas, stun grenades and rubber bullets.

At least 78 Palestinians, most of them civilians, have been killed in Israel's Gaza offensive, Palestinian officials said as militants in the enclave kept up rocket attacks on Tel Aviv, Jerusalem and other cities.

The only Israeli casualties yesterday were two people who had minor wounds when a mortar exploded near the Gaza border.

Israel says it has struck more than 860 targets in an offensive intended to halt persistent rocket fire at its own civilian population.

The rocket fire escalated after Israeli forces arrested hundreds of Hamas activists in the West Bank while hunting for the abducted teenagers.

The offensive followed a build-up in violence after three Jewish students were killed in the occupied West Bank last month and a Palestinian youth died in a suspected revenge attack.