BAGHDAD  Iraqi and American troops seized a rocket launcher loaded with about a dozen Iranian-made rockets aimed at an American base in the southern city of Basra, Iraqi officials said Tuesday.

The United States military said in a statement that Iraqi and American forces conducted a search operation on Basra’s outskirts after hearing explosions near the base Monday night. The American statement said that Iraqi security forces confiscated 16 rockets and arrested three in connection with the operation without giving further details.

No casualties were reported.

A spokesman for the Basra police force, which took part in the operation, said that a rocket launcher loaded with 13 Grad rockets, positioned on the back of a pickup truck, was found in the Shatt al Arab district northeast of Basra. There was no explanation for the discrepancy in the number of rockets.

“They came from a neighboring country,” said the spokesman, Lt. Col. Rafie al-Jawad, but he refused to specify which one.