The leadership... calls on all national and Islamic forces to stand firm against elements who are trying to distort our strong national unity

Palestinian statement

Gaza City was calm on Tuesday, but all its schools and universities, including the Islamic University, the centre of Monday's protests, remained closed.

The BBC's Gaza correspondent Kylie Morris reports that policemen are very visible on every street corner.

She says there is an intelligence van parked outside the building where the BBC and other foreign media have their offices, monitoring their movements.

Foreign journalists outside the Gaza Strip have not been allowed to enter since Monday's riots, and Erez checkpoint has been sealed off on the Palestinian side.

Agitators blamed

The violence followed the first US-led strikes on Afghanistan and a broadcast on al-Jazeera television by Bin Laden, America's chief suspect for the 11 September attacks on New York and the Pentagon.

Dozens were wounded in the Gaza Strip

Palestinian leaders set up an investigation and blamed agitators for sparking the violence.

A statement said: "The leadership regrets these painful incidents.

"It calls on all national and Islamic forces to stand firm against elements who are trying to distort our strong national unity."

On Tuesday, Palestinian students in the West Bank protested against the use of force by their police in Gaza.

Sit-ins were staged at the universities of Nablus and Bethlehem, and students held up banners reading "We will not allow Palestinian blood to be shed by Palestinians" and "No to political arrests."

About 1,500 students from Nablus's al-Najah University marched, carrying banners protesting US air strikes and international sanctions on Iraq.

Israel, for its part, praised the behaviour of the Palestinian police.

"For the first time we congratulate the Palestinian Authority for taking the measures which it promised to implement against terrorists," said Raanan Gissin, spokesman for Israeli Prime Minister Ariel Sharon.

Angry individuals

The BBC's Gaza correspondent said Tuesday's demonstrations were not actually organised by the radical groups Hamas or Islamic Jihad, but were rather a spontaneous protest of angry individuals - a much greater threat to the Palestinian Authority than organised opposition.

For the first time we congratulate the Palestinian Authority for taking the measures which it promised to implement against terrorists

Israeli spokesman Raanan Gissin

Witnesses said the casualties came when police fired live bullets at the crowd.

Police sources say it was masked gunmen who killed at least two of the three - a 13-year-old boy and a 21-year-old student of Gaza's Islamic University.

Doctors said a third demonstrator was clinically dead on a life support machine.

Police stations attacked

About 5,000 people took part in the protest, many chanting slogans against the United States and Israel, urging Bin Laden to strike Tel Aviv.

A 13-year-old and a 21-year-old were killed

Palestinian leaders had wanted to prevent a repeat of the anti-US demonstrations which took place after the 11 September attacks.

If police were responsible for the deaths, it would be the first time Palestinian security forces had killed Palestinians during the current year-long uprising against Israel.

The human rights group Amnesty International has called for a public inquiry into the Gaza violence.