Madeleine, whose parents have Irish roots, disappeared from her family's holiday apartment in Praia da Luz in the Algarve 10 days ago. Police say all evidence points to an abduction.

"Today is our daughter Madeleine's fourth birthday, " said Alex Woolfall, a representative for the holiday company used by parents Gerry and Kate McCann, speaking on their behalf yesterday.

"We would like to mark it by asking people to redouble their efforts to help find Madeleine."

Police ended a physical search for Madeleine in the area immediately around the Praia da Luz resort reported that police are now looking for two men and a woman who were filmed on security cameras with a young girl at a petrol station not far from the resort where Madeleine disappeared. The car is believed to have a British numer plate.

Newspapers and television have reported the same trio may have been at the same beach as the McCanns a few days before the kidnapping, taking pictures of Madeleine. One witness near the beach had reportedly complained of his child being photographed.

On Friday, footballer David Beckham made a televised appeal for her release, and a British millionaire has offered �1m to anyone who finds Madeleine. Woolfall said such offers had given the McCanns hope. "On Madeleine's birthday, please keep looking, please keep praying, please help bring Madeleine home, " he said in a televised statement.

In the UK, Madeleine's aunt, Philomena McCann, whose mother comes from Donegal, told BBC television yesterday the girl's parents were having a family day to mark their daughter's birthday. "We are going to have small celebrations, not of Maddy's birthday, but of her life so far, " she said.

Relatives of missing Madeleine McCann also joined 60,000 fans at the Scottish Premier League match between Celtic and Aberdeen yesterday.

Players from both clubs wore yellow armbands during the game at Celtic Park in Glasgow. Supporters also held up posters of Madeleine.

Celtic said yesterday's gesture was intended to keep the focus on the search for the missing girl.

A Celtic spokesman said: "We were approached to wear the yellow armbands and naturally we were very happy to agree to this. Hopefully, this will keep the focus on the search for Madeleine.

"Clearly, the thoughts of everyone at the club are with Madeleine and her family at this extremely difficult time and, of course, we are pleased to be able to offer any kind of help or comfort that we possibly can.

"We cannot begin to imagine how Madeleine's parents feel at this moment, which is why it is important everyone in Portugal and throughout Europe does everything they can to bring her home."

Gerry McCann worked for Celtic before moving to England.