U.S. ambassador James McGee and diplomats from Britain, the European Union, Japan, the Netherlands and Tanzania were questioned for about 45 minutes at a police checkpoint outside the capital Harare on Tuesday.

They were also held up at a rural hospital where they visited victims of post-election violence and were questioned by officials about their reasons for being there. The United States condemned Zimbabwe's "harassment" of the diplomats.

Mugabe's spokesman George Charamba told the state-run Herald newspaper the incident was of serious concern.

The Herald accused the envoys of "circumventing diplomatic protocol" and going on a "spirited campaign to demonise the government ahead of the presidential election run-off".

Official results of the disputed March 29 election showed Morgan Tsvangirai of the opposition Movement for Democratic Change (MDC) beat Mugabe in the presidential poll, but not by enough votes to avoid a run-off.

In a parallel parliamentary election held on the same day, Mugabe's ruling ZANU-PF party lost its majority to the opposition for the first time since independence from Britain in 1980.

"The presence of several journalists from private-owned media houses in his (McGee's) convoy appeared to confirm suspicions that the 'fact-finding missions' have largely been stage-managed to come up with 'cooked up evidence' of political violence" in support of the opposition, the Herald said.

The government has accused the MDC of being a Western agent.

"NOT ABOVE THE LAW"

The newspaper, which tends to reflect official thinking, said the diplomats had breached a rule that prohibited them from travelling more than 40 km (25 miles) outside Harare without prior clearance from the Foreign Ministry.

"In Zimbabwe, even mighty America is not above the law of the land. We have rules and regulations," Charamba said.

The United States, a major donor of aid to Zimbabwe, has been a strong critic of Mugabe, accusing him of harassing and attacking the opposition. The MDC says 32 of its supporters have been killed in the violent aftermath of the March polls.

ZANU-PF denies it is behind the violence and accuses the MDC of instigating attacks.

In a separate article in the Herald, the head of a pro-government lawyers' group urged it to consider imposing a state of emergency to quell the violence.

"Literally, Zimbabwe is at war with foreign elements using local puppets," said Martin Dinha, the head of Zimbabwe Lawyers for Justice. "Western countries are known to fuel violence, civil wars and strife in Africa and the Middle East. Zimbabwe must not fall into the trap of the evil nations' agenda."

Tension in Zimbabwe is rising ahead of the run-off, which Tsvangirai said he would contest even though he believes he won the vote outright. He accuses the government of vote-rigging, an allegation it denies.

A date for the run-off has not been set and Tsvangirai remains abroad despite pledges to return home to prepare for the vote. The MDC leader left Zimbabwe shortly after the elections and has been on a tour of regional states to garner support.