Thirteen people have been killed and eight wounded in a car bomb attack on a market located in Baghdad, an Interior Ministry official said.

The blast occurred at 7:45pm on Thursday on the outskirts of Baghdad's western Kadhimiyah neighbhourhood, the official said.

In a separate attack on Thursday, armed men killed the brother of a top Sunni Arab politician in Baghdad on Thursday, members of his Iraqi Islamic Party said.

Mahmoud al-Hashimi, brother of Iraqi Islamic Party leader Tariq al-Hashimi, died on Thursday, according to senior party official Ayad al-Samarei. He refused to give further details.

Al-Hashimi is being tipped as the speaker of the new parliament, which is scheduled to meet on Monday.

Thursday's attacks come at a time of growing sectarian tension which has raised fears of civil war.

The Islamic Party is one the country's main Sunni political organisations.

Bahjat al-Samarei, a local Sunni official, said Mahmoud al-Hashimi was driving with a friend in eastern Baghdad when armed men opened fire, killing them both.

Police confirmed such an attack occurred but could not confirm the victim was al-Hashimi's brother.

Earlier this month, two other prominent Sunni politicians said close relatives had gone missing. One of them blamed al-Qaida in Iraq for trying to frighten them into abandoning their roles in government.

Khalaf al-Ilyan, head of the National Dialogue Council, reported the disappearance of his brother and niece in Ramadi, an anti-government stronghold west of Baghdad.

The other Sunni politician, Saleh al-Mutlaq, said his brother disappeared in Salahuddin province, north of Baghdad.

PHOTO CAPTION

A member of an Iraqi security force guards the site of a car bomb after a suicide attacker drove up to a busy vegetable market. (AP)