Youths infuriated by a lack of political reforms rioted in Tonga's capital Thursday, attacking the prime minister's offices, overturning cars and setting fires that destroyed businesses downtown, officials and witnesses said.

Australia said it would consider sending security forces to the South Pacific nation if the government requested it, after overwhelmed police were left standing by as gangs of youths roamed the streets of Nuku'alofa smashing windows and looting shops.

Some semblance of control began returning to the city late Thursday after hours of unrest, as police started moving bystanders out of the central business district.

But as night fell, fires burned unchecked and looters moved unchallenged through the streets with apparently stolen goods, Mary Fonua of the Matangi Tonga news Web site told The Associated Press.

Witnesses estimated more than half the city's central shopping area had been razed by fires that spread from building to building in high winds.

"We're a little busy here," an unnamed police spokeswoman said when asked to comment on the carnage. The phones of government and other officials didn't connect or rang unanswered.

Australia and New Zealand, regional powers in the South Pacific that head a peacekeeping force in the Solomon Islands after rioting there earlier this year, condemned the unrest.

Australian Foreign Minister Alexander Downer said he spoke to Tonga's Prime Minister Fred Sevele by telephone earlier Thursday and would be in touch again Friday.

"He would like us to keep a close eye on the situation there," Downer said. "Whether we would need to provide additional security, we are not sure yet at this stage."

Downer, who is attending the Asia Pacific Economic Cooperation forum in Hanoi, Vietnam, said the situation had quieted down somewhat, though "there are people running around the streets."

The unrest erupted after thousands of people met in Tonga's capital, demanding that parliament pass democratic reforms before it ended its annual session on Thursday.

Windows were smashed in Sevele's offices, Parliament House, the Magistrates' Court, the Public Service Commission Office and the Finance Ministry. It was not known if the prime minister was in his office at the time.

Rioters overturned shelves and stripped stock from a mid-city supermarket owned by Sevele and looted shops owned by Chinese and other businessmen of alcohol and other goods, Fonua said.

Fonua said the office of the Shoreline power company had burned to the ground along with a hotel, and that the Pacific Royale Hotel had been "trashed" by hundreds of rampaging youths.

"It's a full-fledged riot by protesters," a reporter told New Zealand's National Radio, adding that Chinese shops in villages near the capital had also been looted and torched.

Police were helping to get people out of the area safely, and trying to protect property. But they made no effort to arrest rioters, Fonua said.

The disturbance follows a rally in the capital in support of democratic change in the near-feudal South Pacific kingdom.

Tonga radio and television said the youths were believed to be pro-democracy supporters, unhappy about what they claim is the delay in implementing reforms.

Reporter Martini Tapueluelu told New Zealand's National Radio a letter read to protesters, allegedly from Sevele, agreed to demands that democratic change occur by 2008, when 21 of the nation's lawmakers would be elected by popular vote.

Sevele, who is appointed by the king, is seen as complicit in delay of the reforms, along with most of the nation's political establishment.

Last month, a government committee recommended all lawmakers in Tonga be elected. Only nine lawmakers in the 32-seat parliament are now elected by popular vote — with the rest appointed by the king and noble families.

The recommendation was a significant step in accelerating efforts to reform the kingdom's political system since the September death of King Taufa'ahau Tupou IV, who was in power for more than 40 years.

Tonga's King Siaosi Tupou V was believed to be at a royal villa outside the capital Thursday.

New Zealand Foreign Minister Winston Peters called the violence "a disaster for Tonga ... and a severe setback at a time when political reform is happening."

A protest "had corroded into acts of arson ... but there is no way anybody interested in political reforms will advance their cause by criminal actions," he told National Radio from the APEC meeting.

Tonga, located halfway between Australia and Tahiti — has a population of around 108,000 and an economy dependent on pumpkin and vanilla exports, fishing, foreign aid and remittances from Tongans abroad.