The attacks are shaking Iraqis' confidence in the security forces
At least 11 people have been killed and more than 11 wounded in bomb attacks on two minibuses near the southern Iraqi town of Kut, police say.
They said the bombs, which were attached to the buses, exploded on the road between Kut and Baghdad.
Kut is in a mainly Shia area some 150km (95 miles) south-east of the capital.
The attack comes days after a double truck bombing in Baghdad killed at least 95 people, the deadliest strike in Iraq this year.
Those bombings left many Iraqis doubting the government's claims to be getting on top of the violence, the BBC's Andrew North reports from Baghdad.
Police initially said more than 20 people were killed in Monday's blast, but the head of the Wasit provincial council later confirmed the lower toll in what he called "a criminal and treacherous act".
"This is an effort to bring violence to the province and create terror," said Mahmoud Abdulla.
Maamum Thajil, a mortuary official at Zahra hospital in Kut, told AFP news agency that four women and two children were among those who died.
There has been an escalation of attacks in Iraq since US troops pulled out of urban areas at the end of June.
But the overall level of violence has fallen since peaking in 2006 and 2007.
Attachable bombs, which are known as "sticky" or "magnetic", are commonly used by Iraqi insurgents.