Six crew members have died after an Iranian merchant ship capsized in Kuwaiti waters, Iran's official news agency IRNA reported Tuesday.

"The Arabakhtar I ship, whose six crew members were of Indian and Iranian nationality, sank on Sunday," Nasser Passandeh, head of Iran's port and maritime navigation authority, was quoted by IRNA as saying.

The report did not say what caused the Sunday incident, and an Iranian official said search operations were still ongoing to locate three of the victims' bodies.

Three bodies had been retrieved in a joint effort between Iran and Kuwait, Passandeh said.