At a time of drought, skyrocketing food prices, crippling inflation and intensifying street fighting, many of the aid workers whom millions of Somalis depend on for survival are fleeing their posts – and in some cases the country.

They are being driven out by what appears to be an organized terror campaign. Ominous leaflets recently surfaced on the bullet-pocked streets of Mogadishu, Somalia's ruin of a capital, calling aid workers "infidels" and warning them that they will be hunted down.

Since January, at least 20 aid workers have been killed, more than in any year in recent memory. Others have been abducted.

The attacks add a chilling dimension to the crisis in Somalia, which has unfolded over the past 17 years and grown increasingly violent as outside forces, including the U.S. military, have turned a civil war into a more international conflict.

U.N. officials are especially worried by the recent attacks because they say Somalia is heading toward another full-blown famine. Without professional workers to distribute food or tend to the sick, the country could sink into a catastrophe reminiscent of the early 1990s, when hundreds of thousands of people starved.

"This couldn't be happening at a worse time," said Peter Smerdon, a spokesman for the U.N. World Food Program.

The attacks on aid workers – including Westerners, Somalis working for Western organizations and Somalis working for local groups – have escalated this month.

Two weeks ago, a high-ranking U.N. official was shot as he stepped out of a mosque. Last Sunday, an agent in charge of transporting emergency rations was killed. On Thursday, three elders who were helping local aid workers distribute food were shot to death.

It is not clear who is behind the terror campaign or whether it is connected to previous assassinations of journalists and intellectuals. The leaflets and accompanying e-mail messages sent to several aid organizations seem to signify a new degree of organization.

Several factions of Somalia's Islamist movement, which is fighting an intense guerrilla war against the government, have condemned the attacks.

Jeffrey Gettleman,

The New York Times