BAGHDAD, Iraq - Insurgents exposed the vulnerability of Iraq's security forces again Sunday, killing at least 22 national guardsmen and their driver in a suicide bombing and 10 other people in separate attacks with elections just weeks away. Prominent Shiite leaders called for unity with Sunni Arabs wanting to delay the vote but insisted it be held despite the violence.
Also, the U.S. military sent new forces to counter the threat in Mosul, center of a worrying rise in car bombings and raids in recent weeks.
Secretary of State Colin Powell later repeated past warnings of more violence ahead of the Jan. 30 elections for a national assembly, and the guerrillas have made good on those fears with tragic ease. Iraq's poorly equipped security forces usually have far less training than American troops, and attacks on them usually result in more casualties.
The worst attack Sunday occurred in Balad, 50 miles north of Baghdad, when a suicide bomber detonated his explosives-laden vehicle next to a bus carrying Iraqi national guard troops.
Police Lt. Haidar Karar said 18 guardsmen and the driver were killed in the initial blast and four more guardsmen later died of their wounds.
U.S. officials said they were still trying to determine if there were one or two attackers inside the car that detonated next to the bus.
It was the deadliest assault on Iraqi security forces since October, when insurgents gunned down about 50 new national Guardsmen at a fake checkpoint. Another national guardsman was killed separately, south of Kirkuk, officials said.
The car bomb detonated as the bus passed a U.S. base in Balad, U.S. military spokesman Maj. Neal E. O'Brien said. Balad is in the so-called Sunni Triangle, the scene of frequent assaults on U.S. and Iraqi security forces.
"Those responsible for suicide attacks are seeking to halt Iraq's progress on the path to democracy," O'Brien said.
The Shiite leaders who spoke Sunday belong to the Unified Iraqi Alliance, a mainstream Shiite coalition running in the election.
The group was expected to do extremely well in the election and its leaders likely will have top government posts if the vote goes through.
They reached out to Sunni Arabs, many of whom are boycotting the vote and have sought a delay, and called for talks to avert civil war.
