Zimbabwe's opposition party asked the United Nations Saturday to intervene in the country's presidential runoff campaign over fears that longtime ruler Robert Mugabe may stage a violent crackdown to stay in power.

The opposition Movement for Democratic Change also was to appear before Zimbabwe's High Court to try to force the country's election commission to publish the results of the March 29 election, party spokesman Nelson Chamisa said.

Independent projections show the MDC candidate, Morgan Tsvangirai, won most of the votes cast in the election but not enough needed for an outright victory over Mugabe.

The ruling ZANU-PF party announced Friday it was endorsing Mugabe, whose 28-year rule led Zimbabwe from liberation to ruin, in a runoff election.

Chamisa said there were signs that Mugabe, 84, was preparing to use violence to keep his hold on power. He pointed to a march in Harare by war veterans loyal to Mugabe who have beat up opponents in the past; a raid on opposition party offices; and the detention of foreign journalists by armed police in full riot gear.

"They are trying to intimidate people, they are trying to set up the context for unleashing violence. The vampire instincts of this regime are definitely going to come out," Chamisa charged.

Zimbabwe needs the assistance of the international community, he said.

"The U.N. has to make sure that there is no violence in this country. ... They should not (wait to) come when there is blood in the street, blood in the villages."

Mugabe has ruled since his guerrilla army helped bring about an independent Zimbabwe in 1980. His popularity has been battered by an economic slide that followed the often-violent seizures of white-owned commercial farms since 2000. A third of the population have fled the country, 80 percent of those who remain are jobless and inflation is more than 100,000 percent.

Chamisa said he expected the court to answer its petition for the election results immediately in Saturday morning's hearing, but he was not hopeful of the outcome.

Zimbabwe's courts are stacked with Mugabe sympathizers who have delayed hearing opposition challenges to results of 2002 and 2005 elections that international observers said were marked by fraud and intimidation.

The U.S. and other Western nations also have been pressing for the presidential results to be announced.

The law requires a runoff within 21 days of the first elections. But diplomats in Harare and at the United Nations said Mugabe was planning to declare a 90-day delay to give security forces time to clamp down.

An African Union election observer team found no evidence of fraud during voting last weekend, according to the delegation's leader, former Sierra Leone president Ahmed Tejan Kabbah.

Kabbah praised Mugabe as "a patriot," and said during a meeting Thursday that the Zimbabwe leader was "relaxed" despite his setback at the polls.

New York Times journalist Barry Bearak was among those detained Thursday by heavily armed riot police who surrounded and entered a Harare hotel frequented by foreign reporters, lawyers said. The U.S.-based National Democratic Institute said one of its staff, American Dileepan Sivapathasundaram, was detained at Harare's airport as he tried to leave the country Thursday.

The government had rejected most foreign journalists' applications to cover the elections and had barred Western election observers.

Lawyer Beatrice Mtetwa said the attorney general decided there was no case against the two Americans and a third person who was not identified. However, police decided to hold them. It was not clear whether new charges would be filed.

State Department Tom Casey said four Americans were detained Thursday, but two had been released and were leaving the country. He said one of the two still in custody was a reporter and had been seen by U.S. officials. The other had not been located by U.S. officials, he said.