Singapore police said on Friday they had arrested 21 people following a rare street brawl involving members of a small opposition political party.
Police were called in after a fight broke out on Thursday among members of the Singapore Malay National Organisation, a marginal party that has never won a seat in parliament.
Four members were taken to hospital for injuries suffered during the brawl, in which hammers and screwdrivers were used.
Press reports said the dispute stemmed from a power struggle within the party.
Those arrested could face caning and jail terms of up to 10 years if found guilty of rioting and being armed with a deadly weapon. All are out on bail, a police spokesman said.
Street brawls are rare in Singapore, a city-state known for its low crime rates.