A Reuters witness in Kyrgyzstan's second-biggest city said supporters of Bakiyev, toppled in last month's violent revolt, scuffled with guards and entered the government building after holding a demonstration that drew about 1,000 people.

Any worsening of tensions in Osh, at the heart of Central Asia's most flammable and ethnically divided corner, would be of concern to regional powers keen to maintain stability in a country home to a US and a Russian military air base.

"Yesterday... they planned to storm the parliament and declare a new government," Omurbek Tekebayev, a deputy prime minister in the interim government, told Reuters.

On Wednesday, the government faced its first large public protest in the capital, Bishkek, as hundreds of opponents, many of them members of Bakiyev's Ak Zhol party and the allied Communists, demonstrated against the dissolution of parliament.

Tekebayev said unrest in Osh, where police had to intervene to end a brief brawl between the supporters and the opponents of the new government, was part of the same plan.

"This (plan) has failed in Bishkek and today they tried to do it in Osh," he said.

Tekebayev said the interim government had sent Defense Minister Ismail Isakov to Osh and that government supporters were rallying forces there.

"He (Isakov) has full authority and has the right to make any decisions he deems necessary at the moment," Tekebayev said.

Protesters in Osh have brought a pro-Bakiyev regional governor, sacked by the interim government, into his former office which they have occupied.

The interim government is made up of Bakiyev opponents who have accused him of ordering troops to fire on protesters during last month's upheaval, as well corruption and nepotism during his five-year rule.

Bakiyev fled and his opponents claimed power in Kyrgyzstan after protesters stormed government buildings in Bishkek in early April. At least 85 people were killed in clashes between protesters, some of them armed, and police who fired into crowds.

The interim government has struggled to stamp its authority across the impoverished, predominantly Muslim ex-Soviet republic, particularly in Bakiyev's southern power base.

Bakiyev initially fled to the south and sought to muster support after his overthrow, but later left for Kazakhstan and then took refuge in Belarus. He insists he remains president but has said he would not seek to return in that role.

The US base at Bishkek's Manas airport is key to US efforts to supply forces fighting in nearby Afghanistan.

Moscow and Washington have both expressed support for the interim government, which has promised to hold new parliamentary elections in October.