Party Secretary-General Tendai Biti told a news conference that tallies based on totals posted outside polling stations showed Movement for Democratic Change leader Morgan Tsvangirai had won 50.3 per cent of the vote and Mugabe 43.8 per cent.

Biti said a second round runoff was not necessary but the MDC would accept one “under protest”. Election rules say any candidate needs an absolute majority for an outright first round victory.

Biti appealed to Mugabe, president for the last 28 years, to concede defeat and avoid “embarrassment”. Mugabe, 84, faced an unprecedented challenge in Saturday’s elections because of the economic collapse of his once prosperous country.

Mugabe’s Government immediately rejected the MDC victory claim as “mischievous”.

Deputy Information Minister Bright Matonga told Sky television: “President Mugabe is going nowhere. We are not going to be pressurised into anything.”

The Government has warned that victory claims before an official result would be regarded as a coup d’etat.

Matonga said in a telephone interview with Sky: “No-one is panicking around President Mugabe. The army is very solidly behind our president, the police force as well.”

He added: “We are not going to be rushed by anybody. They can make statements left right and centre, but they are merely wasting their time.”

No official results of the presidential poll have been issued four days after the election and Mugabe has not been seen in public since voting, despite speculation he would make a television address on Tuesday night.

Biti said MDC tallies showed it had also won the parliamentary vote, taking 99 seats to the ruling ZANU-PF’s 96.

The latest official results gave ZANU-PF 93 seats to 91 for the MDC with five for a breakaway Opposition faction.