The incident occurred during the band's performance on July 29, when members Robert Del Naja and Grant Marshall held up a Palestinian flag on stage and shouted "Free Palestine", with some audience members reportedly joining the chant, the BBC reported.

In a joint statement, the Singapore Police Force and the Infocomm Media Development Authority (IMDA) said investigations had been completed, and the authorities had decided to issue stern warnings to both musicians.

"Upon completion of investigations and after careful consideration of the facts and circumstances of the case, the Police, in consultation with the Attorney-General’s Chambers, administered stern warnings to both men for offences under Section 3 of the Foreign National Emblems (Control of Display) Act 1949 and Section 16 of the Public Order Act," the statement said.

The authorities added that both men have been banned from re-entering Singapore.

The IMDA is also investigating whether the band breached several conditions attached to its concert licence and said appropriate action will be taken once the probe is complete.

According to the statement, one of the licence conditions explicitly prohibited the display of flags supporting any cause. Despite the event organiser acknowledging those conditions beforehand, the two band members displayed a foreign flag on stage, and one of them shouted "Free Palestine" during the performance.

"IMDA will also not grant any future application for performances by the band in Singapore in view of the entry ban," the statement added.

Massive Attack is currently on a world tour, with its Singapore performance being the only scheduled stop in the city-state.

The group has long been known for taking public political positions on a range of issues, including the war in Gaza.

Massive Attack comprises Robert Del Naja and Grant Marshall.

Earlier this year, Del Naja was arrested while taking part in a demonstration in London. According to the BBC, he was accused of showing support for Palestine Action, an organisation that has been proscribed in the UK.