According to the country's police authority, this violates the strict law that no foreign flags or other national symbols may be displayed in public.
The two band members, who were not named in the police statement, are not allowed to re-enter Singapore and have also been given a "stern warning".
The British trip-hop band has long been outspoken in its criticism of Israel's war in Gaza. In April, frontman Robert Del Naja was arrested in London during a pro-Palestinian demonstration, and the band has also been a driving force in a music boycott of Israel and has campaigned to prevent their songs from being streamed within the country.
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