BASRA, IRAQ (REUTERS) - A rocket struck the site of the residential and operations headquarters of several global major oil companies, including US giant ExxonMobil, near Iraq's southern city of Basra early on Wednesday (June 19), wounding three people, Iraq's military said.

There was no immediate claim of responsibility. It came after two separate attacks in as many days on bases housing US military personnel in Iraq, as tension rose between the United States and Iran.

The rocket hit the Burjesia site west of the city, according to police and a statement released by the military. Police earlier said two Iraqi workers were wounded.

The United States evacuated hundreds of diplomatic staff from its Baghdad embassy last month, citing unspecified threats from Iran against US interests in neighbouring Iraq, where Teheran supports some Shi'ite militias.

Wednesday's incident came just as Exxon staff who were also evacuated after the diplomats' departure had begun to return to Basra.

A security source said Exxon was evacuating 21 foreign staff immediately by plane to Dubai.

Oil officials said operations including exports from southern Iraq were not affected by the incident.

Other companies operating at the site include Royal Dutch Shell and Italy's Eni, the oil officials said.

The rocket was a short-range Katyusha missile, the military said. Police said it landed 100m from the part of the site used as a residence and operations centre by Exxon.

Burjesia is near the Zubair oilfield operated by Eni.

Washington has ramped up sanctions pressure on Iran in recent months and says it has sent additional forces to the region over tension with the Islamic Republic.

It blames Teheran for attacks on tankers in the Gulf of Oman last week. Teheran denies it was involved.

Both sides say they do not want war, but analysts warn that such incidents could escalate violence in the region.