The bomber drove his car into the funeral procession for a slain Kurdish official, Sayid Talib Sayid Wahab, on Sunday.
Wahab, who belonged to Masud al-Barzani's Kurdistan Democratic Party (KDP), was killed by anti-government fighters three days ago, according to Abd al-Ghani Yihya, a Kurdish official in Mosul.
Deputy provincial governor and KDP spokesman Khisru Goran, speaking from Mosul, said the car ploughed into the funeral tent and exploded, but the US military said it was not a suicide attack.
About 30 people were killed and more than 50 wounded, the US military said.
US troops, Iraqi police and ambulances raced to the scene, but unidentified armed men blocked the road and fighting broke out, Goran said.
Basra, Baghdad bombs
A huge explosion rocked the southern city of Basra late on Sunday evening, Aljazeera reported.
Three blasts and one shooting incident rocked central Baghdad late on Sunday, killing at least one civilian, Iraqi police officials said.
Bomb blasts have become a fact
of daily life in many Iraqi cities
One Iraqi was killed and two others wounded when two roadside bombs exploded near a small amusement park in central Baghdad, an Iraqi police official said on Sunday.
The first explosion occurred outside an amusement park in the Baghdad neighbourhood of Zayuna.
About 20 minutes later, another blast took place in the same area, near a gas station outside al-Shaab athletic stadium, but did not cause any material damage, the police official said on the usual condition of anonymity.
Also late on Sunday in the Yarmuk district in the west of Baghdad, a roadside bomb attack wounded two Iraqi policemen, who were evacuated to a nearby hospital, Major Musa Abd al-Karim said.
Unidentified armed men opened fire on an Iraqi police patrol in the Ghazaliya district, also in Baghdad's west, Abd al-Karim added.
One of the police officers was wounded and the assailants escaped after the attack, he said.
Earlier on Sunday, fighters shot dead five Iraqi police officers at a checkpoint, and a car bomb has killed four people in Baghdad, police said.
Sergeant Andrew Miller, a US military spokesman, said a total of six car bombs exploded in Baghdad on Sunday, wounding at least five American soldiers.
Australian Defence Minister Hill
was in Baghdad on Sunday
Meanwhile, an Australian citizen has been taken captive in Iraq, according to a videotape delivered by his captors to news agencies on Sunday.
On the two-minute video, the sandy-haired man identifies himself as Douglas Wood, a 63-year-old, who lives in California and is married to an American.
He calls on US, Australian and British authorities to withdraw from the country.
"My captors are fiercely patriotic. They believe in a strong, united Iraq looking after its own destiny," Wood said, his head slumped forward and his voice close to breaking.
Wood says on the tape that he has worked in Iraq for more than a year and says that he "has done many jobs with the American military". It is not clear what sort of work he does.
A statement from the captors issued with the tape said it had been released to coincide with a visit to Iraq by Australia's Defence Minister Robert Hill, who was in Baghdad on Sunday.
The authenticity of the tape, which carries the banner of a previously identified group calling itself the Shura Council of the Mujahidin in Iraq, could not be verified.
In other developments, US and Iraqi forces raided a suspected fighters' hideout near Baghdad and arrested 11 people thought linked to the killing of Irish aid official Margaret Hassan, police and British officials said.
Iraqi police said the raids happened near the town of al-Madain, about 40km southeast of Baghdad and a scene of frequent attacks in recent weeks.
Margaret Hassan was kidnapped
in October 2004
They said 11 people were detained, five of whom had admitted complicity in the murder of Hassan.
Hassan, who was head of CARE International in Iraq, was kidnapped in October. She was killed about a month later.
"We are aware that a raid was conducted and that items were recovered that we believe may belong to Margaret Hassan," a spokesman for the British embassy said.
"There is reasonable evidence to believe that the items were Hassan's. ... But until our police have finished their investigation we cannot say definitively."
He said British police, many of whom are based in Iraq and assist with training Iraqi security forces, were investigating but could not say when their investigation would end.
Investigators have uncovered a mass grave in southern Iraq containing as many as 1500 bodies, most of them thought to be Kurds forcibly removed from their homes in the late 1980s.
The site, near the town of Samawa, about 300km south of Baghdad, consists of 18 shallow trenches dug by earth-moving vehicles into hard limestone rock.
The US military said rockets
killed three civilians in Falluja
Most of the victims were women and children who were apparently lined up in front of the pits and shot with AK-47 assault rifles, according to a US investigator.
About 110 bodies have been excavated from the site, nearly two-thirds of them children and teenagers.
They are being forensically examined and evidence gathered will be used to build cases against Saddam Hussein and his top deputies for war crimes, crimes against humanity, and genocide.
The site was first identified early last year by the US Coalition Provisional Authority in Iraq, but proper examination did not begin until early this month and finished on 24 April.
On Saturday, fighters fired at least seven rockets into the city of Falluja, killing three Iraqi civilians and wounding another, the US military said.
Two mortar shells were also fired into Falluja, about 50km west of Baghdad, but caused no casualties, the military said in a statement.