WASHINGTON -- The US military struck missile launch sites and mine-laying boats in southern Iran on Monday, the US Central Command said.

"US forces conducted self-defense strikes in southern Iran today to protect our troops from threats posed by Iranian forces," Tim Hawkins, spokesperson for the command, said in a statement.

"Targets included missile launch sites and Iranian boats attempting to emplace mines. US Central Command continues to defend our forces while using restraint during the ongoing ceasefire," he said.

The strikes were carried out in the Bandar Abbas area which hosts Iran's main naval base, destroying two vessels of Iran's Islamic Revolution Guard Corps and hitting a surface-to-air missile site, said Hawkins.

Four people were killed in the attack, while the total number of casualties remained unclear, Fars News Agency reported, citing Iranian state television.