The extreme measures taken by the Palestinian Authority since Monday's protests in support of Osama Bin Laden show how seriously Yasser Arafat is taking the situation.

In response to the public anger over the killing of three Palestinians by Palestinian police, officials have announced they are to hold an investigation into what happened.

Mr Arafat has been travelling abroad for talks on the Afghan crisis

They are also urging the population to keep calm, warning that any further violence would be contrary to the national interest.

In addition, officials are continuing to keep foreign journalists out of Gaza.

The last thing Mr Arafat wants is for the international press to witness the wrecked police stations and other evidence of popular anger.

Nor does he want Western journalists asking what people think of Osama Bin Laden.

It was bad enough when, in the aftermath of the 11 September attacks against America, TV cameras showed some Palestinians in Gaza celebrating.

Bin Laden's message

Now, from the Palestinian leader's point of view, the situation has been made much more volatile as a result of Bin Laden's skilfully-timed broadcast on the popular al-Jazeera TV station on Sunday.

His warning that America would never enjoy peace until there was peace in Palestine was welcomed by many Palestinians, tired of what they saw as the weakness of Mr Arafat and the other Arab leaders.

Bin Laden is seen as the new champion of the Palestinian cause

Especially in Gaza's overcrowded refugee camps, where hope is in short supply, Bin Laden is seen as the new champion of the Palestinian cause.

On the day after the broadcast, university students in Gaza organised a march to denounce America and show their support for Bin Laden.

Palestinian police responded with live ammunition, killing three people including a 13-year-old boy.

Grievances coalesce

Amnesty International has criticised what it calls the reckless and unlawful use of lethal force by the police.

What is clear is that a number of Palestinian grievances are now coalescing.

The anti-Israeli, anti-American mood is still extremely strong more than a year after the start of the intifada.

There is simmering discontent with the perceived corruption, ineffectiveness and human rights abuses of the Palestinian Authority.

And now, on top of everything else, there is the Afghanistan crisis.

US lifeline

Yasser Arafat's position was already fragile before the attacks of 11 September.

Now, with America waging a global war against terrorism, he is under even more intense pressure to rein in Palestinian violence.

There will need to be direct American intervention in the Middle East if Palestinian and Israeli leaders are to be induced to keep a lid on the ongoing violence

After Monday's protests he has warned that anyone, young or old, breaking the officially-declared ceasefire - announced two weeks ago, after a much-delayed meeting between Mr Arafat and Israeli Foreign Minister Shimon Peres - will be arrested.

To achieve a degree of calm, the Palestinian leader now badly needs two things.

He needs relative calm, and to achieve this he will have to crack down on Islamic militants, as the Israelis and the Americans have been pressing him to do for months.

And he needs President Bush to throw him a lifebelt.

In other words, there will need to be direct American intervention in the Middle East if Palestinian and Israeli leaders are to be induced to keep a lid on the continuing violence - and perhaps move, gradually, back to the negotiating table.

The stakes are perilously high.