Bombs killed a farming couple and a policeman in separate attacks Wednesday in northern Iraq, officials said.

One man and his wife were killed at about 5:30 a.m. while working in their orchard in the Diyala province town of Sadiyah.

Police said they don't think the bomb was targeting the couple but was left behind by insurgents who long controlled the area.

Also Wednesday, a car bomber struck a patrol, killing a policeman and wounding two others in the northern city of Mosul.

Insurgents remain active in Diyala and Mosul despite security gains and an overall decline in nationwide violence. Many were believed to have fled north to escape U.S.-Iraqi military operations in Baghdad and surrounding areas.

The officials spoke on condition of anonymity because they're not authorized to release the information.

In southern Iraq, authorities believe they have found another mass grave from Saddam Hussein's regime.

Local villagers found two skulls, bones and old clothes in the oil-rich Nahran Omar area northeast of Basra.

The director of the local human rights commission, Mahdi al-Timimi, said excavation for more remains will start Thursday. He could not comment on how many remains might be unearthed.

Several Saddam-era mass graves have been unearthed since the dictator was ousted following the 2003 U.S. invasion.

The latest discovery caused a temporary halt to oil exploration in the section being excavated.

The victims were believed to have been killed in 1991 when Saddam's forces brutally crushed a Shiite uprising following the Gulf War.

Saddam's cousin known as "Chemical Ali" al-Majid and another former Baath party official Abdul-Ghani Abdul-Ghafur were sentenced to death late last year after being convicted for their roles in the operations against the Shiites.

Ten other defendants were sentenced to jail in the same case and three were acquitted.