Ariel Sharon was under increasing international pressure tonight to call off his West Bank siege of Yasser Arafat even as the Israeli army stepped up its campaign.

A Palestinian sniper opened fire on Israeli soldiers and civilian cars at an army checkpoint in the West Bank, killing 10 people, the army and hospital officials said.

Israel has killed six Palestinian policemen in a series of raids on four West Bank towns and villages today.

Israeli tanks and bulldozers have invaded the West Bank town of Jenin for the second time in two days, destroying the remainder of a police compound they attacked yesterday.

Israel's use of American-made warplanes in the Middle East conflict has brought new charges from Palestinians that the US Government is leaning heavily in Israel's favour.

Israeli jets have fired missiles at Palestinian security buildings in three towns in apparent revenge for a Palestinian attack on an Israeli army base in the Gaza Strip yesterday.