Security forces, which had not previously moved against the protestors, staged operations to remove protestors from government offices in Jalal-Abad and Osh, both around 250km southwest of the capital Bishkek, provoking violent clashes.

"Several demonstrators were injured during the assault by special police forces against the headquarters of the Osh regional administration, and four later died in hospital," an official from the opposition Popular Movement told AFP.

However, Kyrgyz State Secretary Osmonakun Ibraimov denied the report, saying that "there are no casualties", only several wounded policemen and "naturally there are injured among the civilians, as the most aggressive protesters attacked the police and probably got a few punches."

"The opposition, those who organise these rallies, profit by spreading such lying rumors, to excite people even further," Mr Ibraimov said in comments broadcast by the Russian Moscow Echo radio station.

Some 60 people were arrested in the assault, officials said earlier.

In Jalal-Abad, groups of protestors set fire to a police station and stormed the regional governor's offices, as around 10,000 people rallied outside to demand the release of protestors arrested earlier for occupying the building.

Around 2000 protestors armed with sticks, stones and Molotov cocktails and using a bus as a battering ram broke into the police compound next to the office and freed around 30 of the arrested protestors.

With a section of the police compound ablaze, some 700 protestors re-took the governor's office, hanging banners from the windows demanding President Akayev's resignation as they had done for two weeks prior to Sunday's arrests.

Outside in the city's tree-lined main square two cars and a bus were set on fire.

Police opened fire to warn off the crowd, injuring one protestor in the leg.

But Jalal-Abad's Deputy Governor Almaz Asanaliyev defended the police's response and said no one had died either in the shooting or subsequent fire.

"We didn't fire at the people... not one person died," Mr Asanaliyev told AFP. "The majority of these people were drunken, hot-tempered young men."

Russian media reported there had been deaths on both sides from the clashes, with Russia's Channel 1 speaking of a "possible death toll of 10 to 16".

Interfax news agency, citing law enforcement sources in Jalal-Abad, said the toll could be as high as 10. "For the moment the exact number of dead is not known, but it could be as high as 10."

There was shock among residents of this town of 80,000 people overlooked by the snow-capped Ferghana mountain range.

"It's awful, the police station is still burning - tomorrow there will be more people here," a retired state employee living in a one-storey wood-framed house close to the town square said.

Sunday's events came amid a wave of unrest in this mountainous republic over parliamentary polls that went to a second round on March 13 and that the opposition has accused Mr Akayev's administration of rigging.

Mr Akayev has repeatedly warned of the possibility of civil war in the event of attempts at a Western-backed "people power" uprising of the kind seen in two other former Soviet republics, Georgia and Ukraine, within the last 18 months.

While protests have barely touched the capital, tensions have long run higher in the south of the country, which borders Uzbekistan and saw major inter-ethnic clashes in the Soviet Union's last months in which hundreds died as well as fatal shootings of six protestors allegedly by police in March 2002.

The parliamentary polls have been particularly tense as Akayev, the country's only post-Soviet leader, has vowed to stand down at presidential polls due late this year. Opposition figures suspect he could try to extend his term or hand-pick a successor.