BAGHDAD, Iraq – A man wearing an explosive belt blew himself up yesterday outside a bank in the northern city of Kirkuk, police said, killing at least 20 bystanders and wounding 83, many of them women and children, in the deadliest single suicide bombing in Iraq in more than a month.

In Kenaan, a town between Kirkuk and Baghdad, a suicide car bomber killed five Iraqi soldiers at a road checkpoint and a mortar attack left the town’s police station in flames, the Associated Press reported.

And in restive Anbar province, west of Baghdad, police found 24 bodies dumped in two separate areas in Habbaniya.

Kirkuk’s police chief, Major General Torhan Yousif, said the bomber was carrying more than 100 pounds of explosives when he joined a line of people waiting in line at the government-run Rafidain Bank to pick up their paychecks. The explosion killed and wounded civilians, police, and employees of local political parties, as well as severely damaging the bank and surrounding shops.

“The street was full of blood of the wounded and killed, and all the shops closed because people were afraid of more attacks,” Nawzad Omar, 50, said afterward at a local hospital.

The Associated Press reported that children and street vendors selling products from sugar to kitchen utensils were among the people killed, according to an official at the hospital where the victims were being brought, Captain Salam Zangana.

The oil-rich city of Kirkuk, situated about 160 miles north of Baghdad, has been a scene of frequent violence in the past two years. It is populated by ethnic Kurds, Arabs, and Turkmen, and all three groups are attempting to establish dominance.

Under Saddam Hussein’s rule, the government expelled Kurds by the thousands from Kirkuk and re-populated the town with Arabs from other areas. But with the fall of Hussein in April 2003 and Kurdish parties’ strong showing in national elections this year, Kurds have returned to Kirkuk and are bidding to make it the capital of their autonomous northern region.

Mr. Yousif said the bank and the line outside had been heavily guarded yesterday but that the bomber somehow skirted the security forces. “This is considered a major security flaw, for which all the security plans should be looked over again,” he said.

The attack claimed more lives than any single bombing since May 6, when a suicide car bomb killed 31 people in Suwayra, south of Baghdad.