Shootings and a bombing killed six people in Iraq on Tuesday, including four police in the main northern city of Mosul, security and medical officials said.

With the latest attacks, at least 139 people have been killed in Iraq in the past week -- more than died in attacks in the entire month of May, according to official figures.

Three police were shot dead with silenced weapons near a school in west Mosul, while a police first lieutenant was killed by gunmen near his home in the city's north, police First Lieutenant Khaled al-Juburi said.

Dr Mahmud Hadad of Mosul General Hospital confirmed the toll.

In Palestine Street in Baghdad, gunmen shot dead the owner of a currency exchange shop and wounded his son, an interior ministry official said.

A medical source said that Al-Kindi hospital had received one wounded person and one body.

In the Tarmiya area north of Baghdad, a civilian was killed and five others wounded when an explosives-rigged bicycle exploded, the interior ministry official said.

In the Sadr City area of the capital, gunmen wounded police Lieutenant Colonel Rahim Kadhim, the official added.

The past week has seen a wave of deadly attacks in Iraq.

On Wednesday, 72 people were killed in attacks across the country. Two days later, gunmen killed at least seven people, and 32 people were killed in two car bombings targeting Shiite pilgrims in Baghdad on Saturday.

On Monday, a suicide bomber killed 22 people at a Shiite mourning gathering in Baquba, north of the capital.

Violence in Iraq has declined dramatically since its peak in 2006-2007, but attacks remain common. A total of 132 Iraqis were killed in violence in May, according to official figures.