Protests have taken place around the world to demand intervention to end the fighting in Sudan's Darfur region.
Campaigners say time to help Darfur is running out
Organisers of the Global Day for Darfur said events were taking place in 35 capitals to mark the fourth anniversary of the conflict.
Protests included a rally in Downing Street in London, as well as a march on Rome's Coliseum and a demonstration in the German capital Berlin.
Some 200,000 people have died since the conflict began, according to the UN.
Celebrities backing the campaign, such as George Clooney and Mick Jagger, have signed a statement accusing the international community of apathy.
Under the slogan "Time is up... protect Darfur", demonstrators will turn round some 10,000 hourglasses filled with fake blood to highlight the continuing violence in Darfur.
At the London event, Kristyan Benedict from Amnesty International said: "In certain parts of Darfur, blood is running like water.
"It's a horrific scene in Darfur, and this is just meant to be one of those representations that show what's really going on."
A letter addressed to the British Prime Minister Tony Blair called for him "to use your influence to push the international community to call for action".
Other events include a day of cultural events in Cairo including the showing of a documentary called Jihad on Horse Back containing victims' testimony, and a demonstration outside the Sudanese embassy in Abuja, Nigeria.
The statement signed by celebrities calls on the world to "end its stalling and take decisive action".
What was originally a conflict between the Sudanese government and rebel groups in Darfur opposed to it has now spilled over into Chad and the Central African Republic.
Last year the government of Sudan agreed in principle to accept a joint African Union/UN peacekeeping force but Khartoum wants the force to be mostly African in composition and for the African Union to take the leading role, not the UN.
There has been a lot of diplomatic debate between Washington, Beijing, New York and Khartoum recently as international pressure is brought to bear on Sudan's government, BBC UN correspondent Laura Trevelyan notes.
The US and the UK have been persuaded to hold off on imposing sanctions against the Sudanese government for now to see if Khartoum does shift significantly and allow for a major deployment of peacekeepers.