At least 70 people have been killed and scores more injured in a double bombing at a university in Baghdad.
A car bomb blew up outside Mustansiriyah University and a suicide bomber targeted students as they fled.
The attack came as US President George W Bush defended his decision to send thousands more troops to Iraq.
In a TV interview, he expressed frustration at the ongoing violence, but said the bloodshed would get "a lot worse" if the US did not step in.
Last week Mr Bush ordered 21,500 additional US troops to Iraq, mainly to Baghdad, for a new security drive to rid the city of daily sectarian attacks.
"If we don't crack this now, the violence will spiral out of control," he said in an interview on the PBS programme NewsHour with Jim Lehrer.
He blamed al-Qaeda for triggering the sectarian violence, saying it was "important for the American people to understand it is al-Qaeda that is doing a lot of these spectacular bombings".
His comments came as the UN said more than 34,400 Iraqis had died in 2006 in violence across the country, more than three times the Iraqi government's estimate.
In other violence:
- At least 25 people died in car bombings and shootings in Baghdad
- Twenty-five unidentified bodies were found in Baghdad
- Four US soldiers died in a blast in Nineveh province on Monday, the US military said
The BBC's Mike Wooldridge in Baghdad says the bombers apparently attacked at the front and rear entrances of the university building, catching many of the students as they emerged.
A car bomb exploded followed by a suicide bomber who blew himself up among people fleeing the first blast in the predominantly Shia area, police said.
Pictures from the campus showed a scene of devastation, with wrecked and blackened vehicles scattered across a wide area.
"The majority of those killed are female students who were on their way home," Reuters news agency quoted a university official as saying.
"There's glass everywhere and the doors were blown out," the official said.
Police said 170 people were wounded in the blasts, the worst single attacks in the capital this year.
The Ministry of Higher Education has issued a plea for blood donors.
Iraqi Prime Minister Nouri Maliki blamed the attack on "a hopeless group of Saddamists and extremists".
Hours earlier, another twin bombing tore through a used motorcycle market in Baghdad's mainly Shia Bab al-Sheik neighbourhood.
An initial blast drew in onlookers, who were hit by a second explosion moments later.
"The first explosion - many people died and the people who came to rescue them were killed in the second explosion," an unnamed witness told the Associated Press news agency.
"There was a motorcycle that exploded in the second blast," he said.
Raad Abbas, 26, described a scene of carnage.
"Shortly after midday, I heard an explosion. Motorcycles were flying in the air, people were falling dead and wounded," he told AP.
Meanwhile in the north of the capital, gunmen opened fire on shoppers in the mixed al-Bounuk area, killing 10 and wounding seven others, before reportedly fleeing in vehicles.