Guerrillas shot down a US helicopter in Iraq yesterday, killing at least 13 soldiers and wounding 20 people in the bloodiest single strike on US-led forces since they invaded Iraq to oust Saddam Hussein.

The crippled Chinook helicopter came down in farmland at 9 a.m. near the village of Baisa, south of Falluja, a fiercely anti-US town 50 km (30 miles) west of the capital.

?Currently 13 soldiers are KIA (killed in action) and some 20 wounded?, a US Army spokesman said. US helicopters circled above the smoking wreckage. Other helicopters and US Humvee vehicles were parked nearby.

Some Iraqis were jubilant. ?The Americans are pigs. We will hold a celebration because this helicopter went down ? a big celebration?, said wheat farmer Saadoun Jaralla near the crash site. ?The Americans are enemies of mankind.?

It was the third time guerrillas had brought down a US helicopter since US President George W. Bush declared major combat over in Iraq on May 1. The Americans invaded in March.

Bush himself had vowed on Saturday to stand firm and said leaving Iraq prematurely would strengthen the ?terrorists? who were to blame for recent deadly suicide attacks.

A US spokesman said two Chinooks had been heading for Baghdad airport with troops on a rest and recreation break when one of them was ?shot down by an unknown weapon?.

A witness in Falluja, Dawoud Suleiman, said: ?There were two American helicopters. They fired a missile at one and missed, and then they hit the other, which crashed and caught fire.?

US troops told journalists to leave the area as a military medical helicopter with a Red Cross sign on its side landed, sending up clouds of dust from the dry scrubland.

Before the helicopter attack, 123 US soldiers had died in hostilities in Iraq in the past six months, including one killed by an overnight roadside bomb blast in Baghdad and two killed by a bomb in the northern city of Mosul the day before.

Rising death toll

Rocket and bomb attacks have killed 12 US soldiers in an eight-day upswing in violence that began when guerrillas rocketed a Baghdad hotel where US Deputy Defense Secretary Paul Wolfowitz was staying last Sunday.

The next day four suicide attacks killed 35 people at the International Committee of the Red Cross office and three police stations, prompting the United Nations, the ICRC and other aid agencies to pull more foreign staff from Baghdad and review their operations, in a fresh blow to reconstruction efforts.

The commander of US-led forces in Iraq has sought to minimise the importance of the burst of guerrilla activity.

?The coalition has maintained its offensive focus in the face of what we regard as a strategically and operationally insignificant surge of attacks,?Lieutenant-General Ricardo Sanchez told a news briefing on Saturday.

There was no let-up in the attacks yesterday. In Falluja, residents said a roadside bomb had hit a convoy of US personnel in civilian vehicles. At least one vehicle was ablaze at the scene, where gloating crowds shouted anti-US slogans. Television pictures showed a gleeful youth wearing a US Army helmet. Others danced on wreckage.

In Baquba, northeast of Baghdad, residents said a roadside bomb had exploded as a US convoy passed, hitting a bus carrying university students and wounding two women.

Several of Iraq?s neighbours held security talks in Damascus, mindful of US assertions that Syria and Iran were not doing enough to prevent foreign militants crossing into Iraq.

Iraq?s interim foreign minister, Hoshiyar Zebari, said he would not accept a belated invitation to attend.

Officials at his ministry said Syria had been reluctant to invite him because of misgivings about being seen to recognise Iraq?s US-backed interim government.

?It?s impossible for us to make it, and that was their intention,? Zebari said yesterday. ?We don?t even know what the agenda is.?

US troops and Iraqi police had tightened security in Baghdad and other cities over the weekend in response to rumours that guerrillas planned another series of bombings.

Many fearful parents kept their children out of schools for a second day. The deputy headmistress of the Baghdad Middle School for Girls said only a fifth of 750 pupils had turned up.

?They?re staying away because they?re afraid of explosions. We?ve tried to assure parents that it?s safe,? she said.

By Michael Georgy