GERMISTON, South Africa - Aid groups struggled yesterday to feed and shelter thousands of immigrants chased from their homes by attacks on foreigners, while critics said the government must shoulder some blame for the violence.

David Stephens, acting secretary-general of the South African Red Cross Society, said he was preparing for a long-term crisis, working with international and local groups, and government officials to coordinate aid efforts. He said unofficial estimates of the number of displaced ranged as high as 13,000.

Zimbabweans, Malawians, Mozambicans, and others from neighboring countries have been the main targets.

They came to South Africa, the region's economic hub, looking for work and ended up sharing squatter camps with poor - and increasingly frustrated - South Africans.

The Institute for Race Relations blamed the government, saying its policies had "created a tinderbox of unmet expectations which exploded."

The institute cited a long list of factors: a failure to clamp down on violent crime; corruption; inadequate staffing and low morale among the police; a lack of real job-creating policies; poor delivery of government services, and porous border controls.