Brazilian police have arrested 16 leaders of the country's landless peasants' movement for occupying the president's family farm, despite a deal to let them go free.

The leaders were seized as they withdrew peacefully from the property as part of a settlement to end the 24-hour occupation aimed at pressing demands for land redistribution.

The two government officials who helped end the 600-strong invasion of the land belonging to President Fernando Henrique Cardoso's sons have expressed anger at the arrests and offered to resign.

MST activists frequently clash with the authorities

Witnesses said the 16 were handcuffed and placed on the floor before being driven away in a police van, the Reuters news agency reported.

It is thought that the leaders are being taken to the capital, Brasilia, for questioning about the farm invasion.

There has so far been no explanation from the authorities for the arrests.

The BBC's Tom Gibb says they may be related to a conflict over jurisdiction, as the arrests were made by the federal police who the protesters had refused to deal with during the occupation.

Troops and police

The government's ombudsman who deals with land issues, Jesinu Jose da Silva, said he had given his word to the landless leaders that there would be no arrests.

Cardoso's government says the opposition is behind the invasion

The chief negotiator from the Agrarian Development Ministry said she was indignant that their word had been broken.

Brazilian troops and police had been sent to the farm and were earlier reported to be preparing to retake it.

The members of the landless movement (MST) occupied the farm on Saturday to demand that the country's arable land be redistributed from the handful of families who currently own the majority of it.

The protesters began to move out of the property owned by Mr Cardoso's two sons after coming to an agreement with a delegation sent by the government.

'Terrorism'

According to the ombudsman, the MST will get an audience with the Agrarian Development Minister, Raoul Jungmann.

TV images showed the protesters inside the ranch

They will be able to put demands to have credit, running water, electricity and other services for their existing settlements in the area.

The government says it had already assigned another farm in the region for landless families before the invasion took place.

Mr Jungmann accused the movement of terrorism after the protesters moved in early on Saturday, saying they wanted the farm to be given to landless families.

They said they occupied the farm after the authorities refused to discuss their demands.

They also vowed to resist any attempt to shift them by force and threatened to burn down the ranch, about 200 kilometres (125 miles) from Brasilia.

Election issue

The MST has for years been campaigning for major land reform in Brazil.

Our correspondent says the government has been using divide and rule tactics, giving out land to other peasant organisations, and doing its best to discredit the confrontational tactics used by the MST.

At the same time, it is still relatively common for leaders of the MST to be murdered - cases which the police usually fail to solve, our correspondent says.