Parents mark Madeleine's birthday

Missing Madeleine McCann's fourth birthday has passed with her desperate parents still waiting and hoping for her safe return.

With their daughter's disappearance remaining a mystery, Gerry and Kate McCann told the world to "keep looking" and "keep praying" as rewards offered for finding her began to near £3 million.

The McCanns spent much of the anniversary in private and away from the ill-fated Algarve complex where their daughter vanished nine days ago.

As messages of support for the McCanns continued to flood in, a reward of £1.5 million was offered for information leading to Madeleine's safe return.

Entrepreneurs including Sir Richard Branson, retailer Sir Philip Green and Everton chairman Bill Kenwright all contributed to the sum.

But despite the massive rewards, there remains no evidence of firm leads.

Portuguese police are operating under an official news blackout but they have been intensely active with senior detectives working late into the night at headquarters in the town of Portimao.

Nine people, all thought to be British, have been questioned, including the McCanns, who were re-interviewed late into Thursday night and the early hours of Friday morning.

Madeleine's parents issued a simple statement to mark their daughter's birthday.

As well as thanking the public for their support, they added: "We would like to mark today by asking people to redouble their efforts to help find Madeleine. On Madeleine's birthday, please keep looking, please keep praying, please help bring Madeleine home."