A desperate search for a three-year-old British girl continued last night after she disappeared from an upmarket beach resort in Portugal while her parents dined near by.

Despite their half-hourly checks on her as she slept, Madeleine McCann went missing from her parents? rented holiday apartment in the Algarve on Thursday night as they ate tapas only 50 yards away.

Relatives claimed that she had been abducted from the Ocean Club resort, run by the holiday company Mark Warner, in the seaside village of Praia da Luz.

Her parents, Gerry and Kate McCann, both 38-year-old doctors from Rothley, Leicestershire, were being comforted last night by friends and consular officials.

Madeleine, known as Maddy, vanished after being left to sleep between her brother and sister, two-year-old twins.

Mr McCann and his wife, who was clutching Madeleine's pink teddy bear to her chest, made a public appeal last night for the return of their daughter.

Mr McCann said: ?Words cannot describe the anguish and concern we are feeling at the loss of our daughter Madeleine. We now request that if you have any information about Madeleine's disappearance, no matter how trivial, contact the Portuguese police so we can have her back. Please, if you have Madeleine, let her come back to mummy, daddy and her brother and sister.?

The family have moved to another apartment 150 yards from the one from where their daughter is said to have been taken.

The McCanns went to Portugal last Saturday with a group of eight couples, friends said. Mr McCann, a cardiologist, and his wife, a GP, went out for a meal at a tapas bar within the complex at 8.30pm on Thursday, leaving Madeleine sleeping between Sean and Amelie, the twins. The couple checked on their children every half an hour and ensured that the doors were locked, it was said.

The resort offered a creche service but the McCanns chose to leave the children sleeping at the apartment, taking turns to check on them. Between their checks at 9.30pm and 10pm, the apartment was broken into through a window and Madeleine was taken, according to her aunt. Trish Cameron, Mr McCann's sister, from Dum-barton, near Glasgow, said it appeared that someone had been spying on Madeleine and had targeted her for abduction.

?The front door was open, the window had been tampered with, the shutters had been jemmied open and Madeleine was missing,? she said. ?Nothing had been touched in the apartment, no valuables taken, no passports. They think someone must have come in the window and gone out the door with her.?

Police were called at 10.20pm as Madeleine's parents became increasingly anxious. Soon, fellow guests were notified. About 60 staff and holidaymakers searched until 4.30am, while police notified border police, Spanish police and airports.

Three police vans and three police cars were at the scene as officers searched the family's apartment. Others searched the beach 200 yards away.

Specialists fingerprinted the windowsill of the apartment. Sniffer dogs were brought in by Portuguese detectives and unconfirmed reports indicated that Madeleine's scent had been picked up.

The resort caters for 1,000 holidaymakers and is set in lush subtropical gardens. It is made up of self-catering villas and apartment blocks and has several bars and restaurants.

John Hill, the manager at Ocean Club, said that reports that the flat had been broken into had yet to be confirmed.

But Jill Renwick, a family friend, told GMTV that the McCanns were certain that Madeleine had been abducted.

?They were just watching the hotel room and going back every half-hour and the shutters had been broken open and they had gone into the room and taken Madeleine,? she said. ?They went out about 8, went back in at 9, they were fine, went back in at 10 and she was gone.?

Ms Renwick said that it was the McCanns? first holiday of this sort. ?They are very, very anxious parents and very careful, and they chose Mark Warner because it is a family-friendly resort.?

A spokesman for Mark Warner, which has run the resort for two years, said that looking after the McCanns was their priority. ?If necessary, the company will fly other family members out to the Ocean Club. We are all hoping that she is asleep under a bush somewhere and we will find her soon,? he said.

Guests are being asked if they saw anyone acting suspiciously in the area, he said, adding that Mark Warner had never had cases of missing or abducted children before.

He said that Mark Warner offered a baby-sitting service. ?Those facilities were available but, for whatever reason, they were not being used,? he said. Another spokeswoman for Mark Warner said that in the Algarve, unlike most of their resorts, the company did not supply a ?room listening? service, where nannies regularly listen at the door of sleeping children.

John Stephen Buck, the British Ambassador to Portugal, travelled to the Algarve yesterday, as did Craig Mayhew, Mark Warner UK operations director, and a counsellor. The McCanns remain at the police station in Portim?, helping police to piece together what has happened.

A Foreign and Commonwealth Office spokesman said that the Serious Organised Crime Agency was liaising with British and Portuguese police. He added that two officials from the British Consulate in Portim? were with the family.