HARARE, Zimbabwe — Police confronted diplomats seeking to investigate allegations of torture Tuesday, halting their convoy at a roadblock on the edge of the capital. One officer threatened to hit the U.S. ambassador with his car.

The U.S. ambassador, James McGee, was not hurt. Police eventually let the convoy through, and a patrol car escorted them back to the U.S. Embassy before disappearing.

A U.N. official, meanwhile, warned that post-election violence in Zimbabwe is nearing crisis levels, and the opposition Movement for Democratic Change said 32 supporters have been killed — including eight in the last 72 hours.

Tensions have been escalating in Zimbabwe since the March 29 parliamentary and presidential elections.

Opposition leader Morgan Tsvangirai claims he won the presidential race outright, but official results released weeks after the poll showed he did not win enough votes to avoid a second round against President Robert Mugabe.

The opposition has accused the ruling ZANU-PF party of undertaking a campaign of intimidation and violence to pressure voters to cast ballots for Mugabe. Observers have questioned whether a second round would be free and fair with the opposition unable to campaign freely because of attacks and threats. No date for a runoff has been set.

The diplomats involved in the incident at a roadblock on the edge of the capital, Harare, had just completed a tour of hospitals and an alleged torture camp when police demanded they prove they had official permission to visit the sites.

At one point, a police officer threatened to beat one of McGee's senior aides. The officer got into his car and lurched toward McGee after he had demanded the officer's name. The car made contact with McGee's shins, but he was not injured.

McGee climbed onto the hood of the car while his aide snatched the keys from the ignition, then the diplomats used their mobile phone cameras to take photographs of the officer.

McGee insisted the convoy be allowed through and the 11 vehicles passed through after about an hour.

The confrontation was "a message to us, to try to control what we are doing," said U.S. Embassy spokesman Paul Engelstad, who was among around 50 diplomats and journalists on the tour.

Japanese, EU, Dutch and Tanzanian envoys and an Associated Press reporter also were in the convoy.

McGee noted that the government has denied repeated reports from opposition officials and human rights groups of government-orchestrated violence against the opposition.

"The government has said 'Present us with proof.' I think today we have done just that. We do have concrete proof of what is happening in the countryside and the government will have to listen," McGee said.

A priest in the northeast had led the diplomats to a lumber camp occupied by people described to reporters as ruling party militants. McGee said when he confronted them, they hid four notebooks with interrogation schedules.

The priest also led the diplomats to a church hospital where 22 people were being treated for beatings so severe that the flesh had been stripped from their backs. Doctors and nurses said one person had died at the hospital and another three died in nearby villages in the last month.

The diplomats and journalists saw several other victims at a second hospital.

The U.N. resident representative in Zimbabwe, meanwhile, warned of escalating violence in both rural and urban areas.

"There are indications that the level of violence is escalating in all these areas and could reach crisis levels," Agustino Zacarias told reporters.

He said the violence was preventing U.N. humanitarian agencies from reaching people in need and had forced them to scale down operations.

The U.N. representative's comments echoed those McGee made in an open letter published Monday in the state-run Herald newspaper. The letter accused Mugabe's party of orchestrating violence to intimidate opposition supporters before the runoff.

McGee said the U.S. government has received confirmed reports of at least 20 deaths and more than 700 incidents of violence resulting in more than 200 people being hospitalized since the first round of voting March 29.

The paper in turn criticized McGee, accusing him of "very scandalous acts" and of breaching diplomatic procedure by speaking out on the violence that has riven Zimbabwe since the first round.

The Southern African Catholic Bishops Conference said a run-off election would not be possible without an end to the violence and called for international election observers be allowed in to monitor the poll.

"This 'reign of terror' has seen many deaths, savage beatings and flight from family, homes and communities," said Archbishop Buti Tlhagale, president of the religious organization.