Iraq's oil exports are unaffected by the current political turmoil in the country, three sources told Reuters on Tuesday.
Baghdad is seeing its worst fighting for years as clashes between Shiite groups spill into a second day.
Supporters of Shiite cleric Moqtada al-Sadr, have surrounded the 210,000 barrel per day (bpd) Basrah refinery, according to one of the sources.
"If no action from the government, the refinery may have to stop production," the source said.