A 'Demonstration for Democracy' is taking place in London as Zimbabweans head to the polls for presidential elections amid claims of vote rigging.
President Robert Mugabe, 89, and his Zanu-PF party is going head to head with Prime Minister Morgan Tsvangirai and his Movement for Democratic Change (MDC).
Mugabe's promise to stand down as president if he loses the election has been met with scepticism by the MDC.
In London, Zimbabweans are gathering outside the Zimbabwe embassy to call for free and fair elections.
The protest has been organised by Action for Southern Africa (ACTSA), the Trades Union Congress and the Zimbabwe Vigil.
They have identified several sources of "major concern" surrounding the elections, including an increase in reports of intimidation and harassment.
They complain of inaccuracies in the voter roll.
"The voters roll contains inaccuracies. According to estimates there are over two million young people, particularly from urban areas, missing, and over 100,000 aged over 100 on the roll," said the ACTSA.
"Over a quarter of constituencies have more registered voters than inhabitants. Some parties have complained that they have not been given a copy of the roll until a couple of days before the election."
The campaigners also voice concern over political bias in state institutions and say there are inadequate numbers of domestic and international election observers.
Tony Dykes, Director of Action for Southern Africa said: "Zimbabwe is going to the polls today with few of the crucial reforms that it needs for free and fair elections in place. Sadly there are already signs that the poll will not be free and fair.
"Today we are standing in solidarity with the people of Zimbabwe as they vote, supporting their right to elect their leaders without the fear of violence, harassment or an electoral system that is rigged to favour one party over another."
