BAGHDAD — A rocket hit the Green Zone in Baghdad on Sunday night, home to Iraqi government offices and those of other foreign governments, where tensions were already high amid a standoff with Iran.

No one was hurt, said Gen. Yahya Rasool of the Baghdad Joint Command, which includes American and Iraqi forces. He confirmed that a Katyusha rocket had landed in the heavily fortified zone and said it had been fired from across the Tigris River.

The American Embassy said that there was no damage to American facilities and that no one had claimed responsibility.

The explosion rattled residents of the Green Zone, who said that the strike set off alarms at the United States Embassy. The heavily guarded compound was already on a heightened state of alert after nonemergency personnel there and at the United States Consulate in the northern city of Erbil were ordered last week to leave.