Washington  - The US said it was "deeply troubled" by continuing "intimidation and violence" in the southern African nation of Zimbabwe, and called for the United Nations to "immediately" take up the issue.

The call came in a statement issued late Thursday by the White House.

Zimbabwe was "in clear violation" of the election standards for the Southern African Development Community (SADC) - the regional economic and political grouping - the White House said.

Decades-long Zimbabwe President Robert Mugabe is trying to hang on to power in a run-off election June 27 against opposition leader Morgan Tsvangirai. His security forces re-arrested Tsvangirai again on Thursday, along with the secretary general of the group, the Movement for Democratic Change, Tendai Biti.

"We believe the time has come for the United Nations Security Council to take up immediately the issue to prevent further deterioration of the regions humanitarian and security situation," the White House press secretary said in a statement.

Earlier Thursday, the US accused the Zimbabwean government of intercepting a shipment of food aid and dishing it out to ruling party officials.

Twenty metric tons of the food was taken off a truck near Bambazonke and then given to Zanu-PF party officials during a rally on June 6, said Gonzalo Gallegos, a US State Department spokesman.

"What we had here was the Zimbabwe military and police officials hijacking a truck that was carrying 20 metric tons of humanitarian food aid that was directed for hungry Zimbabwean children," Gallegos said.

Also on Thursday in New York, the top UN coordinator for emergency humanitarian operations, John Holmes, raised alarm about the worsening situation in Zimbabwe, saying the coming harvest would likely only cover one-quarter of the country's needs.

Next week, Haile Menkerios, the UN undersecretary for political affairs in Africa, plans to travel to Zimbabwe ahead of the run-off elections on June 27 against opposition leader Morgan Tsvangirai, who was re-arrested again Thursday as he was campaigning for office. (dpa)