Lovemore Sekeramai, the Zimbabwe Chief Elections officer announces results of the Presidential polls in Harare, Zimbabwe, 02 May 2008

The United States and Britain are questioning Zimbabwe's presidential election results, saying they lack credibility.

Zimbabwe's election commission said Friday that challenger Morgan Tsvangirai beat incumbent Robert Mugabe in the March 29th vote but that a run-off will be needed.

In Washington, U.S. State Department spokesman Tom Casey said the final tally has "serious credibility problems" because of what he called the inexplicably long delays in releasing it.

Britain's Foreign Office said a second election could not be fair unless international monitors were present.

The European Commission also called for international observers to watch a run-off vote to ensure it is "fair" and "free".

Zimbabwe's government banned foreign observers from watching the March elections. It also prevented most foreign journalists from covering the vote.

Both the U.S. and Britain also expressed concern today about reported violence by Mr. Mugabe's supporters against his opponents. U.S. spokesman Casey said that before a run-off election happens, the Mugabe government needs to stop repressing the opposition and others who wish to peacefully express their views.

He said the United States would consult with other countries in the region about how to proceed.

Southern African countries have generally refrained from sharply criticizing President Mugabe or his government.

Some information for this report was provided by AFP, AP and Reuters.