In the deadliest attack, 15 Iraqi National Guard members were killed on the main highway through Latifiyah, about 50km south of Baghdad, Defence Ministry sources said.
Details of the attack were unclear. Some reports stated that the guardsmen were killed in a bomb explosion, but there was no official confirmation, said Talib al-Janabi, an Iraq journalist speaking to Aljazeera.
The driver of the vehicle survived the attack, al-Janabi reported.
Medical sources at al-Mahmudiya hospital said they had received five bodies of National Guard members.
On the same road just outside Latifiyah, five civilians were shot and killed by attackers, said Imad al-Dulaimi, a doctor at a nearby hospital, adding that he had no further details.
Also south of Baghdad, four drivers were killed and four wounded in an ambush on a 14-truck Trade Ministry convoy travelling between Kut and the capital, an Interior Ministry source said.
The route from Kut, 175km (110 miles) southeast of the capital, has become a regular site for attacks on trucks.
Ten Iraqi truck drivers were killed near Hiyt, west of the city of Ramadi, Aljazeera reported on Saturday.
In Baghdad, a deputy to Shia cleric Muqtada al-Sadr was killed in the southern Dura district as he drove to an anti-US protest in the capital, an al-Sadr official said.
Assailants in another car opened fire on Sayyid Fadil al-Shuq, deputy director of al-Sadr's office in the Shia shrine city of Karbala, killing him and wounding another al-Sadr deputy from the nearby city of al-Hur, the al-Sadr official said.
Mosul car bomb
In the northern city of Mosul, a car bomber in an Opel blew himself up. Accounts of casualties differed, with Dr Baha al-Din al-Bakry of the Jumhuri hospital saying two police officers were killed and 13 civilians injured, and medical and police sources telling AFP that one police officer and 14 other people, including 11 officers, were wounded.
In other violence, an Iraqi soldier and a civilian were killed in a roadside bombing in Mashaada, 30km north of Baghdad, said army Captain Asad Saddad.
The Iraqi army and police killed one fighter and arrested three suspected fighters in a morning clash in Balad, 75km north of Baghdad, police said.
The corpses of an Iraqi contractor and a truck driver were found at 5am (0100 GMT) in Dujail, north of the capital. Rebels in the Sunni Muslim heartland north of Baghdad have killed dozens of people suspected of working with the Americans and the new Iraqi government.
In the southern port of Basra, two civilians were wounded at about 9.30am in another roadside bomb targeting an Iraq police convoy in Basra, said Haidar Abd al-Mahdi, a police spokesman.
On Friday, a US soldier was killed in a roadside bomb blast north of Baghdad, raising to 1540 the number of US troops who have lost their lives in Iraq.