A member of Kuwait's ruling family, the grandson of a former emir, was gunned down at a dinner party and a relative was being questioned in the case, a security official said.

"Authorities received a report on Thursday evening that a crime had been committed and the victim was Sheikh Basel al-Sabah," the security official told Reuters.

"The crime took place at the victim's home in Messilah during a dinner party held for a number of sheikhs ... he was killed after being hit by five bullets."

The relative held for questioning was his uncle, Sheikh Faisal al-Sabah, he said.

The Kuwaiti al-Sabah family has ruled the Gulf Arab state for some 250 years, and its head has the last say in political matters in the world's fourth largest oil exporter.

The official gave no word on a possible motive for the killing of Sheikh Basel, 52, who did not hold any government post. His uncle is an army intelligence officer.

The Kuwaiti prime minister has always been a member of the ruling family, and key portfolios such as defence, interior and foreign affairs are also held by al-Sabahs. – Reuters