BASRA, Iraq — Two rockets struck separate targets on Wednesday in oil fields just outside Basra, not far from the headquarters of many international and domestic oil companies.

Though a bit more frequent in recent weeks, rocket attacks have been rare since the Islamic State was pushed out of Iraq more than 18 months ago, and oil fields generally have not been targets. Basra, in southwestern Iraq just above the Persian Gulf, is one of the richest oil production regions in Iraq.

In the first attack, three employees of an Iraqi drilling company who were injured when a Katyusha rocket hit their sleeping quarters were taken to a hospital, said Khalid Hamza, the deputy director of the Basra Oil Company, an Iraqi firm.

There were no injuries reported in the second attack. No other details were available about the strike, and officials would not say who they believed was responsible for the attacks.