Roadside bombs killed three U.S. soldiers Monday in two separate attacks and 16 Iraqis were killed elsewhere, including five teachers and their driver who were shot to death in a classroom by suspected insurgents disguised as policemen.
U.S. and Iraqi authorities, meanwhile, freed 500 detainees from the notorious Abu Ghraib (search) prison in a goodwill gesture to Sunnis ahead of the Muslim holy month of Ramadan (search) and less than three weeks before a referendum on Iraq's draft constitution.
Two of the American soldiers were killed early Monday in western Baghdad, while the third, who was working with the 42nd Brigade, died about 50 miles southeast of the capital, the military said.
The deaths raised to 1,917 the number of U.S. service members who have died since the Iraq war started in March 2003, according to an Associated Press count.
The teachers — all Shiites — were killed as people were leaving the elementary school in Muelha, a village near the town of Iskandariyah (search), police Capt. Muthana Khaled said. Muelha, about 30 miles south of Baghdad, is in a predominantly Sunni area of Iraq.
The five men and their driver were snatched off a minibus as they were leaving the school, Khaled said. All six were then taken back into a classroom, lined up against a wall and shot to death, he said, adding that nobody else was in the room when the killings occurred.
A homicide car bomber also attacked a police checkpoint guarding several government buildings as a private bus carrying 24 oil ministry employees to work in Baghdad, said police Capt. Nabil Abdel Qadir.
The blast killed at least seven policemen and three people on the bus, Qadir said. Fourteen policemen and 22 bus passengers also were wounded, he said.
"The insurgents are targeting Iraqi government employees and worshippers in mosques," Oil Minister Ibrahim Bahr al-Uloum (search) said after rushing to the site. "These savage acts won't undermine the forthcoming people's referendum on the new Iraqi constitution."
The attacks raised this week's death toll to 49 Iraqis and three Americans amid stepped-up violence ahead of the referendum on Iraq's draft constitution, considered an important step in the country's moves toward democracy.
Hours earlier, about 500 detainees left the Abu Ghraib prison on the outskirts of Baghdad on public buses after a brief ceremony.
They were the first of 1,000 due to be freed before Ramadan begins next week, the U.S. military said. Another 1,000 were released from the prison last month.
The military said they were not guilty of serious, violent crimes — like bombing, torture, kidnapping, or murder.
Arab governments often pardon nonviolent offenders during Ramadan, which this year is expected to begin on Oct. 4 or 5.
But it was the first time U.S. and Iraqi officials made such Ramadan releases at Abu Ghraib, which was the center of an international scandal after a number of U.S. military personnel were charged with humiliating and assaulting detainees at the facility.
The move appeared to be part of a government effort to persuade citizens to vote in the Oct. 15 constitutional referendum, particularly the Sunni minority.
Many Sunni leaders and insurgents are calling for a boycott or a "no" vote in the referendum. They say the document would leave Sunnis — who were dominant under Saddam but lost power after his ouster — with far less power than the country's Kurds and majority Shiites.
If two-thirds of voters in any three of Iraq's 18 provinces reject the charter, a new government must be formed and the process of writing a constitution starts over.
The attacks came a day after at least 33 Iraqis were killed in a series of attacks.
On Sunday, gunmen loyal to radical Shiite cleric Muqtada al-Sadr (search) ambushed an Iraqi patrol in an eastern Baghdad slum, and U.S. forces joined a 90-minute gunbattle, killing as many as eight of the attackers in the first significant violence in the neighborhood in nearly a year.
Al-Sadr's militia, the al-Mahdi Army (search), was a stubborn problem for American forces until a truce was negotiated about a year ago that let some U.S. troops pull out of Sadr City to join the November assault on the insurgent stronghold of Fallujah, west of the capital.
Before the truce, al-Sadr's forces had led unsuccessful but bloody uprisings against coalition forces in Kut and the holy cities of Najaf and Karbala, south of Baghdad.
Violence in the poor Shiite district could deepen opposition to the constitution among al-Sadr's supporters, who are bucking mainstream Shiite support for the charter. Shiite unity has been seen as critical for passage of the basic law.
A statement from al-Sadr's office accused U.S. forces of trying to draw them into a battle "aimed at destroying Iraqi towns, particularly those in pro-Sadr areas and .... to prevent al-Sadr followers from voting" in the referendum.
Elsewhere in Baghdad on Sunday, armed men pulled off a daring armored car robbery, killing two guards and escaping with $850,000, and a suicide car bomber slammed into a convoy carrying Interior Ministry commandos, killing seven of them and two civilians.
South of the capital, two separate bicycle bombings in town markets killed at least seven people and wounded dozens Sunday.
In Samarra, 60 miles north of Baghdad, three mortar shells landed in a residential district. One shell hit a house, killing seven members of one family, including children, according to police Capt. Laith Muhammed.