Police hunting for Madeleine McCann have told her parents they received a credible call from a man claiming to know the whereabouts of the four-year-old.

The caller provided such detail that Kate and Gerry McCann put their European search for their daughter on hold in case they needed to act.

The couple were informed of the potential development while in Germany, where they were appealing for information about their eldest child's disappearance.

They hoped that the call was the breakthrough they have been praying for in the five weeks since their daughter disappeared from the family's holiday apartment in Praia da Luz in the Algarve.

The "credible" call was taken from a man who wanted to speak directly to the McCanns, according to a Spanish police source.

It is believed to have been made to police in Spain and was traced to an unregistered pay-as-you-go phone, which appeared to be from a country outside of Europe. The nationality of the caller was not clear.

The couple were preparing to go to Tempelhof Airport in Berlin about 3pm on Wednesday to fly to the Netherlands, but stayed on at the British embassy after being advised that the caller might try to contact them.

At 6pm, journalists travelling in the eight-seater private jet with the McCanns were told there might be a change in destination. The flight crew revealed they had been asked to draw up a new flight plan involving a possible change from Amsterdam to East Midlands Airport.

It was thought that the McCanns might need to go back to the UK to talk to advisers about the call. But all efforts to re-establish contact with the man failed and the couple left Berlin for Amsterdam at 7.30pm.

The McCanns are thought to be on standby, ready to return to the UK if necessary.

A Spanish police source said: "A man called saying he knew where Madeleine was and wanted to speak to the McCanns.

"This did not appear to be a crank call and the information was felt credible enough to warrant the couple being informed immediately."

The McCanns have always said that it might only take one phone call to get Madeleine back.

The possible new lead came as they came to the end of the European section of their search for Madeleine. They have been to Italy, Spain, Germany and the Netherlands in a bid to raise awareness about her abduction. They plan to go to Morocco at the weekend.

The Netherlands was chosen because, after British and German tourists, the largest group of nationals who make up the tourists in the Algarve are Dutch.

Elsewhere yesterday, it was claimed that a Spanish investigative journalist knows who snatched Madeleine.

Antonio Toscano, who specialises in missing persons stories, was quoted by the Madrid daily newspaper El Mundo yesterday saying the abductor is a member of an international paedophile ring which specialises in snatching children.

Mr Toscano said the man was seen in Seville - about two hours' drive from the Spanish frontier with the Portuguese Algarve - about a week before Madeleine disappeared.

El Mundo reported Mr Toscano as saying the kidnapper was working for money with two other people and had served a prison sentence outside Spain for a paedophile offence. Mr Toscano said that he could be working for a European wide international paedophile network.

"Little Maddie was no coincidence and was selected long before her disappearance, probably in Great Britain," Toscano said.

He told the paper he approached a representative employed by the McCanns after learning of the man's possible involvement but was advised to contact Portuguese police. The paper said he contacted the family representative on two other occasions without response.

El Mundo added that Portuguese police have now asked their Spanish colleagues to question Mr Toscano.