Gangs from rival political parties scuffled and threw rocks in East Timor, injuring at least 20 people in what was believed to be the first violence directly related to next month's presidential elections.
Two of those hurt were police officers, said Geraldo da Silva, of the emergency unit in Viqueque hospital, about 135 miles from the capital Dili.
The unrest broke out on Thursday night following a campaign rally by presidential candidate Jose Ramos-Horta, said local police chief Gaspa da Costa.
His supporters brawled with youths aligned with the rival Fretilin, the left-leaning political party of ousted Prime Minister Mari Alkatiri, da Costa said. It was not clear what triggered the dispute.
Eight presidential candidates are midway through two weeks of campaigning. Rallies and speeches are scheduled across 13 districts until a blackout period two days before nationwide polling on April 9.
East Timor, which became Asia's newest nation in 2002, descended into chaos one year ago after Alkatiri dismissed 600 soldiers, a move that split the armed forces into factions and later spilled over into gang warfare. At least 37 people were killed and 150,000 others fled their homes.
The deployment of thousands of international troops helped curb the worst of the violence, and while there have been isolated incidents since then, Thursday's was the first since campaigning began.
The UN police force in the country said in a statement that Ramos-Horta supporters were attacked, but did not say by whom. Fretilin spokesman Filomeno Aleixo said the party did not instigate the violence, but denied involvement.
"Whoever was involved in this incident should be brought to justice," he told The Associated Press.
East Timor voted to break free from 24 years of Indonesian rule in 1999. The country was administered by the United Nations, and until last year's crisis, which led to the overthrow of the government, had been considered a major success in nation-building.