US and Iraqi forces are engaged in fierce fighting in the province with both Shia and Sunni anti-government fighters.
On Monday, nine US soldiers were killed in an attack on a military outpost near Diyala's capital Baquba, one of the worst strikes against US forces since the invasion of Iraq in March 2003.
On Wednesday, a suicide bomber killed nine people when he walked into a police station in Balad Ruz in Diyala.
Shortly after the first blast in Baghdad, a second carbomb exploded in Iraq's Jadriya district, killing six people and wounding at least 18 more.
In northern Iraq, at least three people were killed and 13 wounded in three separate blasts on Thursday in a town near Mosul, 390km north of Baghdad, said a local official who asked not to be identified.
Tens of thousands of US and Iraqi forces have been deployed in Baghdad since February as part of a security crackdown aimed at stopping Iraq from sliding into all-out sectarian civil war.
That crackdown in the capital has prompted fighters to focus their attacks more on provinces outside the capital.
Refugees reach Greece
Greek police have taken 141 suspected Iraqi refugees into custody after their boat arrived in the Greece on Thursday, the country's merchant marine ministry has said.
Officials in the port of Lavrion said there were 13 women and 15 children among the rescued immigrants, who had traveled in a 27-meter fishing boat from the coast of Turkey.
The immigrants were given medical checks at a hospital in Lavrion, 55 kms southeast of Athens, before being taken to state-run hostels, the ministry said.
Four people were arrested on suspicion of smuggling the immigrants.
Hundreds of thousands of Iraqis are believed to have fled their country since the US-led invasion deposed Saddam Hussein, the Iraqi president, in 2003.