Three rockets were fired in the area of the Iraq-Kuwait border on Friday.
Reuters quotes an Iraqi official as saying that they landed inside Iraq and were not aimed at Kuwait or the disputed Mubarak port.
"The rockets targeted the (former) Bucca prison building, which is used by foreign companies," Ali al-Maliki, head of the Basra provincial council's security committee, told Reuters. "Security forces managed to seize the vehicle which was used to launch the rockets."
Basra police spokesman Colonel Kareem al-Zaidi also denied any rockets had been fired at Kuwait's Mubarak port, currently being built on Bubiyan Island.
Shi'ite militia in southern Iraq warned earlier this year they would attack Kuwait if it insisted on building the port.