The British band ⁠Massive Attack said its members were detained by Singapore police and "isolated and separately questioned" after the two performers raised a Palestinian flag ​at their concert in the city-state last Wednesday.

In ​a ⁠statement posted on Instagram on Sunday, the band said they were "surprised and disappointed" that the entire band was detained and questioned.

Several members had their hotel rooms searched and passports temporarily confiscated, the post said.

The trip-hop band has two members, Robert Del Naja and Grant Marshall, both British nationals, who unfurled the flag and held it up as audience cheered "Free Palestine!", a witness said.

Police said last Friday ⁠the ⁠band's actions "could potentially harm the racial and religious harmony in Singapore" and that two band members were issued with stern warnings and barred from re-entering Singapore. Police did not name the two band members.

The band did not say who among the members were detained and whose rooms were searched or passports confiscated.

The band were performing with a live backing band and guest vocalists, including Elizabeth Fraser of ⁠the Cocteau Twins.

"We did not imagine that merely holding up the flag of a sovereign state recognized by 157 countries (Palestine) would violate any law," the band's statement ​said.

"The surreal experience was a reminder of the importance of defending universal ​human rights and freedom of expression wherever those rights are threatened," the band said.

Massive Attack, formed in Bristol in the west of England ⁠in 1988, are known ​for their outspoken political stances, with videos during their concert highlighting conflicts in Iran, Sudan, Gaza and Ukraine.