BISHKEK, Nov 7 (Reuters) Riot police fired tear gas today to break up a brawl between pro and anti-government protesters, the first violence in six days of demonstrations calling for the resignation of President Kurmanbek Bakiyev.

Several hundred opposition protesters shouting ''Bakiyev resign'' fought briefly with stone-throwing government supporters before police on horseback charged the crowd and separated them.

Ambulances took six injured people to hospital, the Health Ministry said.

Opposition leaders accused Bakiyev of trying to provoke them.

''The only way for the government to stop our revolution is to introduce a state of emergency,'' lawmaker Edil Baisalov told reporters.

Baisalov said the opposition had gathered 40 signatures from the parliament's 75 members for its new draft constitution.

The document, drafted during an emergency sitting yesterday night, would strip the president of the power to appoint a government and give it to parliament.

Bakiyev's government denounced it as ''an open attempt at seizing power'' and the president threatened to dissolve parliament if the opposition continued attempts to unseat him.

''Of course if contradictions between the legislature and the executive continue, what will I have left to do? I cannot watch such an orgy,'' Bakiyev told a news conference held jointly with his key ally, Prime Minister Felix Kulov.

The crisis is the deepest of Bakiyev's 16-month rule. Opposition leaders accuse the president of failing to tackle rampant corruption, crime and poverty and say he has broken his promises on reform too often to be trusted.

Opposition protesters waving flags marched again today on the Kyrgyz White House, a seven-storey Soviet-era building which houses the offices of the president and his government.

TROOPS Unlike yesterday, when police guarding the building went over to the protesters' side, there was a heavy troop presence.

Two water cannon stood ready, along with more than 100 regular troops and several dozen aremd commandos in black balaclavas.

A Reuters correspondent at the scene said there were around 2,000 protesters, fewer than yesterday. All kept away from the fence around the White House.

The clashes came when a group of protesters broke away from the White House and returned to the main square, where they encountered a few hundred pro-government demonstrators.

A mountainous ex-Soviet country of 5.2 million people that borders China, Kyrgyzstan is home to both US and Russian air bases.

Washington, Moscow and Beijing jostle for influence in Central Asia.

Bakiyev swept to power after his predecessor Askar Akayev fled the country in March 2005 when a mob stormed his compound.

Fearing a similar fate, the president yesterday announced he had fired his interior minister in an apparent attempt to appease the crowds.

The opposition were not satisfied. Lawmakers gathered in the 75-seat parliament and unilaterally declared themselves a constituent assembly. They then put their signatures to their draft of a new constitution.

The government said the document was not valid. Kyrgyz law states that any changes to the constitution must be approved by at least 51 members of parliament and be subject to a three-month review by the Constitutional Court. It does not allow for the creation of a constituent assembly.

The opposition said they were justified in bending the rules because the crisis demanded quick, decisive action.

REUTERS PB VV1730