Police in Portugal have been told of an attempt to snatch a girl similar to Madeleine McCann just half an hour from Praia da Luz, it emerged last night.

Three-year-old Carolina Santos, who is blonde with blue eyes, was found being led away from the family cafe near the town of Silves by a man last year.

Her parents described yesterday how they had left Carolina playing at the front of the roadside cafe in Fonte de Louseiron, a village around half an hour from Praia da Luz on Christmas Day.

"We were busy working in the kitchen and came out to find out she wasn't there," Abel Santos, 40, said.

"I searched around for her and saw her some way away on the road with a man I took to be Moroccan. We started towards them shouting and Carolina stopped and turned towards us. He disappeared around the bend."

His wife Lina, 28, added: "It was very strange because Carolina is usually very shy and doesn't go with strangers. When I asked her what happened she said he told her that he had another little girl for her to play with. There was no other girl. I was so scared.

"If we hadn't come out at that moment I don't know what would have happened."

They reported the incident to police at the time but say they were told they could not make a formal complaint as no crime had been committed.

A spokesman for the Policia Judiciaria (PJ) said attempted abduction was a crime in Portugal and believed the Guarda Nacional Republicana (GNR) - a separate force - would have filed a report.

Three days ago the couple contacted police again after a Moroccan man threatened to take their daughter during a row at the cafe.

Police said yesterday that they were investigating these incidents, but were not linking them to Madeleine's disappearance, because there were too many dissimilarities.

Meanwhile, signs of frustration began to emerge yesterday at the pace of progress in the hunt for Madeleine.

A source close to the McCann family said that while Madeleine's parents were happy with the "overall thrust" of the investigation, they felt frustrated that concerns they had were not being addressed quickly enough.

Madeleine was abducted on May 3 and despite a huge campaign to make her image known across Europe there has been no news of her whereabouts for three weeks.

As the McCanns prepare to embark on a series of journeys in Europe to boost Madeleine's profile, family members added that the couple were as determined as ever.

The source added: "At every stage throughout this they have been feeding their own questions and concerns back to the investigating authorities through British police and the Portuguese authorities.

"While they remain content with the overall thrust of the investigation they hope their questions and concerns are addressed more quickly."

Portugal's unusual "secret of justice" laws prevent the police releasing information about the investigation publicly and also curtail what they can say even to the family concerned.

The source said: "They fully comprehend the restrictions that the Portuguese legal system places on everyone involved but naturally, as parents who want their little girl back, some of the delays that are occurring are frustrating."

Responding to claims of growing frustration a spokesman for the couple in Portugal said: "At every stage along the way Gerry and Kate have worked with the British and Portuguese police to do everything they can to improve the investigation in ways of taking it forward.

"Gerry and Kate ask on a regular basis what they can do to help the investigation.

"Naturally when it appears that things are moving slowly it can be frustrating - the only thing that would really make them happy is Madeleine's safe return and every parent will understand that."