"We're seeing them in the greatest density," Brigadier General Vincent Brooks told reporters when asked why he kept mentioning Syria when he spoke of foreign fighters in Iraq.

"Whether it's something done by governments we don't know," he said at US Central Command forward headquarters, adding that he had no idea of the numbers of such volunteers.

He said that 300 vests fitted for use by suicide bombers found last week in Baghdad were probably intended for use by foreign fighters.

The comments came amid increasing US charges that Syria continues to back the regime of toppled Iraqi President Saddam Hussein and to sponsor terrorism.

A report in the Washington Post last Tuesday said thousands of Arab guerrilla fighters had made their way to Baghdad, where they try to ambush US and British troops from private homes.

Most of the volunteers cross into Iraq from Syria, it quoted US offciers as saying.

They reportedly come from the Palestinian territories, Egypt, Sudan, Syria, Jordan, Lebanon, Algeria, Yemen and Morocco, according to information collected by US officers from prisoner interrogations and other intelligence.

Judging from a dozen such fighters -- nine Sudanese, two Syrians and an Egyptian -- captured recently by US troops, they are mostly ordinary men lacking military training, except for some from the Palestinian territories, US officers told the daily.

SPACE.WIRE