Demonstrators protesting against war on Iraq will be keeping central London streets clear of traffic on Saturday.

Officers policing the second large-scale anti-war march in as many months have said that major roads will be closed throughout the afternoon for the demonstration in Westminster.

A spokesman for Stop the War Coalition said 200,000 marchers were currently expected for the march.

He admitted, however, that this was not based - as previously - on the number of coaches already booked to attend, but was a 'general feeling'.

Read more from Local London about the Iraq crisis

The demonstration, which aims to allow people 'to express their horror at a war that now looks perilously close', will follow the same route as the vast march on February 15 this year.

There will be an additional setting-off point, however, at Richmond Terrace.

Although not as many people are expected to attend this march, the message from police remains 'don't come into the centre of the capital unless it is absolutely necessary'.

Deputy Assistant Commissioner Andy Trotter, the Met officer responsible for policing demonstrations and festivals, said: "Anyone who was in London on 15 February who didn't attend the march will remember how frustrating it was to have their journey delayed or disturbed.

"Please check traffic restrictions before deciding to come into London this Saturday. If you don't need to come into the centre of town it is probably better to stay away."

The Stop the War spokesman also said the students and school pupils are going out on strike today in protest at military action in the Gulf.

Student unions at both the London School of Economics (LSE) and the School of Oriental and African Studies (SOAS) are expected to participate in the walk-out.

Police advice for marchers and non-marchers this Saturday, March 22 2003:

- If you don't need to come into the centre of town it is probably better to stay away.

- Large crowds move slowly. If you are joining the march please be prepared for a long wait before you set off and be patient with police.

- Check the weather forecast before you set off - it can get very cold when you are standing around, and bear in mind that it has been very wet recently so it is likely to be damp underfoot at the rally in Hyde Park.

- If you are coming with family or friends to arrange a meeting point in case you get separated.

- Bring a portable radio, if you have one, and listen to local radio stations to make sure you get any news relevant to you.

- It may be an idea to bring warm drinks and snacks as you could be out and about for several hours - the rally isn't due to finish until 5pm.

- Please check the media regularly if you are not taking part to try to minimise disruption to your daily lives as much as possible."