LONDON, April 29 (Reuters) - About 700 campaigners took to the streets of London on Sunday as part of an international day of action marking the fourth anniversary of the start of the conflict in Darfur. "Time has run out. We need to act on behalf of the people of Darfur," said European member of parliament Glenys Kinnock. "The international community are not doing enough to help," said Conservative parliamentarian Andrew Mitchell. Police estimated that about 700 demonstrators took part in the demonstration. The United Nations says around 200,000 people have died and 2.5 million have been displaced in the conflict which flared in Darfur in 2003. Rebels say they are fighting the government because it has neglected the region. Centrepiece of the protest was a giant "blood" hour-glass to symbolise what a race against time it is to save people. A letter was being handed in to the Downing Street residence of Prime Minister Tony Blair which said "We urge you to keep the pressure on the government of Sudan until there is an effective peace-keeping force on the ground protecting civilians." In a statement released before the day of action, Blair said: "What is happening in Sudan at the moment is unacceptable, is appalling and is a scandal for the international community. "There are 200,000 people that have died, there are 2 million people that have been displaced, there are 4 million people on food aid. More fighting in recent days further threatens the already fragile situation."