Media playback is unsupported on your device Media caption Madeleine McCann disappeared in Portugal in 2007

UK police probing the disappearance of Madeleine McCann are seeking an intruder who sexually abused five girls in Portugal between 2004 and 2006.

Detectives say the attacks happened in holiday villas occupied by UK families in the Algarve.

The man, described as tanned with dark hair, is suspected of breaking in to 12 properties from 2004 to 2010.

Madeleine was three when she went missing from a holiday apartment in Praia da Luz, Algarve, in May 2007.

The five girls - aged between seven and 10 - were sexually assaulted in their beds.

On one of these occasions, the man assaulted two girls in one villa.

'Serious offences'

Det Ch Insp Andy Redwood said the man had an "unhealthy interest in young white female children" - and tracing him was a priority.

"We need to establish the identity of this man," DCI Redwood said.

Image copyright PA Image caption Two families said the intruder had worn a distinctive burgundy long-sleeved top

"These offences are very serious and no one has been charged in connection with them. We also need to eliminate this man from our enquiries and ascertain whether these offences are linked to Madeleine's disappearance."

Police said the man was bare-chested in some of the attacks, and some witnesses said he had a pot belly. Three victims said he had a "noticeable odour".

Two of the families said the intruder had worn a distinctive burgundy long-sleeved top, and one family said the top had a white circle on the back.

The man was said to have spoken English slowly, with a foreign accent.

While not identical, many aspects of the sexual assaults were similar, police said.

In most of the cases, the intruder appeared in the early hours of the morning and there were no signs of forced entry to the properties.

The suspect may have been in the villa or looking around for some time before committing the offences or being disturbed, either by a parent coming in or the child waking up, officers said.

He remained calm even when disturbed, they added.

The incidents had previously been discounted by Portuguese investigators because they were spread over a wide geographical area and there had been no apparent attempts at abduction.

Media playback is unsupported on your device Media caption DCI Andy Redwood says he needs to hear from other families who may have been affected

Four of the 12 break-ins took place in Carvoeiro, two in Praia da Luz - where the McCanns had been staying - and six in Vale da Parra and Praia da Gale.

There are currently 38 people classed as "persons of interest" linked with the inquiry into Madeleine's disappearance.

It is really critical for us to identify this offender and prove or disprove whether he was involved in Madeleine's disappearance DCI Andy Redwood

Detectives are also sifting through details of 530 sex offenders whose whereabouts are unknown.

Of those, 59 are classed as a high priority, and some of those are British.

Police 'frustration'

Scotland Yard launched a new investigation - codenamed Operation Grange - into Madeleine's disappearance last July, two years into a review of the case, and made renewed appeals for information.

A high-profile campaign run by Madeleine's parents Kate and Gerry McCann, from Rothley, Leicestershire, and a Portuguese police investigation had so far failed to locate the missing child.

The search for Madeleine was given fresh impetus in October when a BBC Crimewatch appeal that aired in the UK, Germany and the Netherlands prompted 5,000 calls.

Image copyright PA Image caption Madeleine vanished from her family's holiday home while parents Kate and Gerry McCann dined at a nearby restaurant

In January, British detectives flew to Portugal and spoke to local police officers there.

DCI Redwood said: "This is an offender who has got a very, very unhealthy interest in young, white, female children who he is attacking whilst they are on holiday in their beds.

"It is really critical for us to identify this offender and prove or disprove whether he was involved in Madeleine's disappearance."

Investigators in the UK have so far sent three international letters of request to Portuguese authorities over the inquiry in to Madeleine's disappearance.

Deputy Assistant Commissioner Martin Hewitt said the slow legal process had caused "frustration".

"We know what we want to do and we are ready to go with that. But the process is the process," he said.

Clarence Mitchell, spokesman for the McCann family, said: "Kate and Gerry still believe that Madeleine is alive and out there to be found, and that is why they are so pleased that the British police are doing such a good job on this."