URGENT precautions have been introduced to stop passengers and crew who might be affected with the potentially deadly Sars virus from embarking on Southampton cruise ships.

Both P&O Cruises and Cunard are now screening passengers and ship board staff to ensure no one with symptoms of the Severe Acute Respiratory Syndrome joins vessels leaving the port.

None of the P&O Cruises or Cunard ships in Southampton is currently sailing to or near any countries that have reported cases of Sars.

One of the city's major operators, P&O Cruises, has so far sent out about 6,000 letters to passengers asking if they have visited an area hit by the virus within the ten days of the beginning of their holiday.

Any people who have returned from Hong Kong, China, Vietnam, Singapore or Toronto, Canada during this period are being offered a full refund on the cost their cruise and asked not to join the ship in Southampton.

As from next Monday, when the company's cruise ship, Aurora, turns round in the port between voyages, passengers will also have to complete and sign a questionnaire confirming they have not visited affected countries.

Crew members, who might have passed through areas with SARS, will not be allowed back on the vessels unless they have been given the all-clear after ten days' quarantine.

A spokesman for P&O Cruises said: "We must stress these are purely precautionary measures as the safety and well-being of all our passengers and crew is our top priority.

"We are taking this illness very seriously. Customers will receive a full refund so long as they can provide proof of travel to Sars affected areas, and we will look at compensation on a case-by-case basis.''

Cunard, which operates the flagship of the British merchant marine, the liner Queen Elizabeth 2 and the cruise ship, Caronia, in and out of Southampton has implemented similar procedures.

A spokesman for Cunard said shoreside medical experts were monitoring the situation closely and each vessel is being provided with regular updates and advice on Sars symptoms and appropriate actions while crew members from countries with the virus are being prohibited from joining the vessels.

"In the interest of extreme caution, Cunard is asking all guests embarking on a cruise to complete and sign a brief questionnaire,'' said the company spokesman.

"Passengers who have travelled within ten days prior to sailing to a country under a Sars related advisory will be evaluated further by our medical staff. Any guests showing symptoms, based on the sole opinion of the medical staff on board will be denied boarding.

"Any guests denied boarding will be offered the option of a future cruise credit applicable to any departure valid for one year from the original sailing date or a full refund.''