Zimbabwe's ruling party edged ahead of the main opposition on Tuesday with over half of parliamentary election results released and concerns grew that President Robert Mugabe was trying to rig the vote.

Riot police in armoured carriers patrolled two of Harare's opposition strongholds overnight and residents were told to stay off the normally bustling streets.

Three days after the most important vote since independence, only 109 out of 210 parliamentary constituencies had been declared, showing the ruling ZANU-PF two seats ahead of the main opposition Movement for Democratic Change (MDC).

No results have been announced for the presidential vote, in which Mugabe faces the most formidable political challenge of his 28 years in power -- from old rival Morgan Tsvangirai and ruling party defector Simba Makoni.

The opposition MDC says it won according to its own tally and has accused the veteran leader of delaying the issuing of the results in a bid to steal the election, which Zimbabweans hoped would ease daily hardships.

Zimbabweans are suffering the world's highest inflation of more than 100,000 percent, food and fuel shortages, and an HIV/AIDS epidemic that has contributed to a steep decline in life expectancy. Mugabe's foes blame him for the economic disaster.

"It is now clear that there is something fishy. The whole thing is suspicious and totally unacceptable," MDC spokesman Nelson Chamisa said.

Mugabe has denied rigging the election and his government warned that any early victory claim would be regarded as an attempted coup.

INTERNATIONAL PRESSURE

An independent Zimbabwean election monitoring group forecast Tsvangirai, leader of the largest faction of the MDC, would win the most votes in the presidential poll but not by a big enough margin to avoid a second round.

The Zimbabwe Election Support Network (ZESN) said its projections gave him 49.4 percent. It predicted Mugabe would win 41.8 percent and Makoni would get 8.2 percent.

Tsvangirai was due to hold a news conference at 0800 GMT, his first since voting ended.

Seven European countries and the United States called on Zimbabwe's Electoral Commission to quickly release the results.

Slovenia, which holds the EU Presidency, also called for a speedy release of the results.

"This would end the current uncertainty and prevent the risk of rising tensions," the EU presidency said in a statement.

Electoral Commission chairman George Chiweshe said the slow pace was due to the complexity of holding presidential, parliamentary and local polls together for the first time.

Although the odds seemed stacked against Mugabe, in power since independence in 1980, analysts believe his iron grip on the country and solid backing from the armed forces could enable him to ignore the results and declare victory.

Marwick Khumalo, head of an observer group from the Pan-African parliament, said the elections themselves were free, fair and credible overall and on Tuesday the African, Caribbean and Pacific (ACP) observer team also endorsed the polls.

"The ACP Election observer mission was particularly impressed by the calm and peaceful atmosphere that prevailed before, during and immediately after polling day," the state-owned Herald newspaper quoted the ACP as saying.

Official results so far showed ZANU-PF with 53 seats, MDC with 51 and a breakaway MDC faction with five. Five of the new seats the MDC won were from traditional ZANU-PF strongholds.

The MDC said unofficial tallies showed Tsvangirai had 60 percent of the presidential vote, twice the total for Mugabe. Private polling organisations also put Tsvangirai ahead.

"In our view, as we stated before, we cannot see the national trend changing. This means the people have spoken, they've spoken against the dictatorship," MDC Secretary-General Tendai Biti said.