At least four people, including two police officers, have been killed in a car bomb attack in Baghdad, the Iraqi capital, police have said.

The bomb went off on Wednesday at about 9.30am (0630 GMT) in Saadun street,  one of the main streets running through the capital.

A string of attacks have occurred in the area in recent days, most of them targeting Iraqi security forces.

In another attack, a roadside bomb blew up at 10am in the Shia-dominated Shaab neighbourhood of north Baghdad, officials said.

Seven people, including three policemen, were injured in that attack.

The attacks follow two days of blasts in Baghdad that have killed more than 30 people and wounded at least 70 others.

Mosul deaths

Meanwhile, in the northern city of Mosul, two Christian sisters have been killed after armed men broke into their home, police said.

The women's mother was hurt in the attack and two policemen were later wounded when a bomb left by the intruders went off as they entered the house.

More than 2,000 Christian families fled Mosul in October after a series of killings in the city.

However, the United Nations High Commissioner for Refugees (UNHCR), said on Tuesday that some were starting to return, with around one-third of the families in one neighbourhood having come back.