Baghdad, Aug 17 (IANS): A Katyusha rocket hit Baghdad's heavily fortified Green Zone, which houses some of the main Iraqi government offices and the US embassy, the military said.

A Katyusha rocket was fired on Sunday from an area located near the al-Nahdha bus station in downtown Baghdad, Xinhua news agency quoted the media office of the Iraqi Joint Operations Command as saying in a statement.

The attack caused no serious damage, the statement said, adding that the security forces found a rocket launcher and defused two more rockets which were ready to be fired.

Meanwhile, an Interior Ministry source told Xinhua that the attack was conducted by two rockets and landed in the zone without causing casualties.

Sirens were heard in the zone as the rockets landed and a helicopter was seen hovering over the area.

The roughly 10 sq-km Green Zone is located on the west bank of the Tigris River, which bisects the Iraqi capital.

No group has so far claimed responsibility for the rocket attack.

The Baghdad airport and the Iraqi military bases housing American troops across Iraq, as well as the US embassy in the Green Zone, have been frequently targeted by mortar and rocket attacks.