The thunderous blast of an Iranian missile was heard throughout Baghdad early today but the explosion, about a mile from the Defense Ministry, apparently did little damage, and no casualties were reported. The 4:30 a.m. blast blew apart a section of bleachers in a soccer stadium.

Iran said the attack on the Iraqi capital was in retaliation for Iraq's air offensive against Tehran and other Iranian cities. An official statement here acknowledged that "an enemy rocket landed at a Baghdad area."

Residents of the capital seemed mildly nervous during the day as they went about their normal business. The shopping streets were crowded despite the oppressive heat. A barrage of threats have been broadcast by Iran warning that Baghdad will be burned and residents should flee to Iraq's holy cities -- Najaf, Karbala, Samarra and Khadimain, which Iran said it has spared from retaliatory attacks.

Between the lines of optimistic interviews and communiques, there are indications of heavy artillery duels, at least, in the nearly five-year-old war, along the southern front near Basra and the central front at Mandali. Requests by journalists for permission to visit these areas have not yet been granted.

But at the scene of the explosion, the mood of the neighborhood appeared one of relief even among the many people sweeping up shattered glass from their shops and middle-class homes.

"Nobody was hurt," was the first remark of several residents in the Amhiya neighborhood.

Even soldiers in the area were relaxed, letting an American reporter, arriving unannounced and unaccompanied, look over the scene. Various diplomats studied the site as well.

Since a similar round of Iraqi bombings and Iranian retaliations with eight explosions in Baghdad two months ago, there has been considerable debate as to whether those blasts were missiles or sabotage.

This morning's explosion appeared to trained foreign observers to be most likely a missile, although the damage seemed less than would have been expected from the old Soviet rockets Iran is reported to have obtained from Libya.

Meanwhile, Iraq apparently continued its air raids against Iran with relative impunity. Iraq said today that its planes struck Tehran twice last night and early today, and that "waves of Iraqi Air Force jets" were sent against four Iranian cities and four military camps today.

Iran's official Islamic Republic News Agency, monitored in Nicosia, Cyprus, said the Iraqi air attacks killed 11 people and wounded 15, The Associated Press reported. IRNA added that "scores" have been killed or wounded in similar attacks on Iranian cities in the past two days.