HARARE, Zimbabwe -- Most white farmers in Zimbabwe stopped working Tuesday, complying with an official deadline ordering them to halt operations in preparation for a government takeover of their land.

Nearly two-thirds of the country's 4,000 white commercial farmers were targeted in the order that took effect at midnight Monday. But many had stopped farming months ago, paralyzed by disruptions caused by the government's "fast track" land seizure program.

The land seizures come as a potentially devastating food crisis looms in southern Africa. In Zimbabwe, the situation is blamed primarily on this year's erratic rainfall and two years of often-violent seizures of land from white farmers by loyalists of President Robert Mugabe.

Despite promises to redistribute the confiscated land to poor blacks, many of the farms have been given to loyal lawmakers and confidantes of Mugabe and ruling party leaders.

In a sign of defiance, two farmers filed lawsuits Tuesday aimed at striking down the government order as a constitutional violation of property and employment rights, said Commercial Farmers Union spokeswoman Jenni Williams.

But there was little hope for court intervention. Mugabe has stocked the courts with loyalists who rarely rule against the government.

Those who break the order could face up to two years in prison or large fines. However, farming officials in the key Chinhoyi and Karoi agricultural districts northwest of Harare reported no efforts by authorities to enforce the deadline Tuesday.

Dairy farmers said they milked their cattle as usual after warning officials that their livestock risked illness if milking was prevented.

Some farmers spent the day packing up personal belongings, including family photo albums and kitchen and household goods, to prepare for the next deadline -- an order to leave their homes by Aug. 8, farmer union officials said.

The European Union has warned that the haphazard redistribution of property in Zimbabwe -- once a breadbasket of the region -- could worsen the impending crisis. The country's mostly white-owned, large commercial farms are about five times more productive than small farms.

The World Food Program estimates that nearly half the country's 12.5 million people would need food assistance this year.

Since June 2000, the government has targeted 5,872 mostly white-owned properties for confiscation -- about 25 million acres.

On many farms already vacated by their owners, livestock, irrigation and other equipment have been seized without compensation being paid.

The state media has warned that security checkpoints would be set up in farming districts to prevent "sabotage" of the land reform program, in an apparent effort to stop farmers from removing goods and equipment from their farms.

Whites make up less than 1 percent of Zimbabwe's population. Until Mugabe's recent land seizures, white farmers -- most of whom are the descendants of British and South African colonial era settlers -- owned about one-third of the nation's productive farmland.

Critics say Mugabe has sped up land confiscations to bolster his waning support and deflect attention from the country's crumbling economy.