BAGHDAD — Iraq’s first lady escaped unharmed yesterday from a bomb attack in downtown Baghdad that struck her motorcade, injuring four body guards.

President Talabani’s wife, Hiro Ibrahim Ahmed, was headed to the city’s central National Theater to attend a cultural festival when her motorcade was hit in the Karrada district, according to the president’s office. It was unclear whether she was the target or the attack was a random bombing.

In fighting Sunday, American troops killed 18 Shiite extremists in unrelenting street battles in the capital’s Shiite militia strongholds of Sadr City, Shula, and New Baghdad.

Iraqi health officials said at least 10 people — including two children — were killed in 24 hours of fighting in Sadr City, a slum of 2.5 million people and a stronghold for the Shiite Mahdi Army militia of the radical cleric Moqtada al-Sadr, who is believed to be living in Iran. It was unclear whether any Shiite extremists were included in the figure because health authorities did not provide a breakdown.

Outside the city, American troops yesterday killed nine Al Qaeda insurgents, including three who were wearing suicide vests, in a clash near Lake Thar Thar in the predominantly Sunni Salahuddin province northwest of Baghdad, the military said. Two other Al Qaeda insurgents were killed in Samarra north of Baghdad on Saturday, it said.

In addition, the American military reported Sunday that 11 Al Qaeda insurgents were killed over the weekend in central and northern Iraq, after a powerful roadside bomb killed four Marines on Friday in the deadliest attack in months in the former Al Qaeda stronghold of western Anbar province.

Amid spiraling violence, Iraqi government spokesman Ali al-Dabbagh and an American spokesman, Rear Admiral Patrick Driscoll, vowed during a news conference yesterday to maintain crackdowns.

Iraq is seeking to increase leverage on Iran, accused by American of financing and training Shiite militants in Iraq and of funneling lethal weapons into the country. Iranian officials have denied the allegations.

Asked about reports that some rockets made in 2007 or 2008 and seized in raids against militias were directly supplied by Iran, Mr. Dabbagh replied: “There is no conclusive evidence.”

A five-member Iraqi delegation returned yesterday from Tehran where they held meetings aimed at halting the suspected Iranian aid to militiamen.

Mr. Dabbagh said Iraq wants friendly ties with Iran and stressed both countries share common interests.

“We can’t ignore or deny we are neighbors. We do not want to be pushed in a struggle with any country, especially Iran,” he said during the news conference.

“We are fed up with past tensions that we have paid a costly price for because some parties have pushed Iraq [in the past] to take an aggressive attitude toward Iran.”

Iran’s Fars news agency reported that Iranian negotiators told their Iraqi counterparts that as long as America carried out attacks against the Mahdi Army in Sadr City, Iran would not restart security talks with the Americans.

Admiral Driscoll said the “multinational force endorses all dialogue,” but he said Iranian involvement in destabilizing Iraq was mostly an “issue between the government of Iraq — a sovereign nation — and Iran to discuss and seek resolution.”