TBILISI — Troops flooded the center of the Georgian capital today to enforce a state of emergency imposed after a violent crackdown on anti-government protesters.

Hundreds of Interior Ministry officers in khaki uniforms and armed with hard rubber truncheons patrolled Tbilisi’s main thoroughfare, the site of the main protests by demonstrators calling for American-backed President Saakashvili to resign.

Riot police responded with tear gas, rubber bullets, and water cannons, and Mr. Saakashvili announced a 15-day nationwide state of emergency, in which news broadcasts on independent stations were halted and all demonstrations banned.

Nearly 100 people hurt during the clashes remained hospitalized today, the Health Ministry said.

Normally noisy, bustling Rustaveli Avenue was quiet. Only a few cars moved along the street.

Many pedestrians seemed stunned by the crackdown, and most were reluctant to talk about it.

“One doesn’t treat one’s own people this way,” a 35-year-old civil servant, Yekaterina Bukoyeva, said. “It was very painful to see how they were dispersing all the people.”

The crackdown followed six days of protests in front of Parliament — Georgia’s worst political crisis since the pro-Western Mr. Saakashvili was elected nearly four years ago.

The American-educated Mr. Saakashvili, who is trying to shake off centuries of Russian influence and integrate the ex-Soviet republic with the West, accused Moscow of fomenting the protests and expelled three Russian diplomats. Tensions with Russia have risen as Mr. Saakashvili has sought to establish central government control over two separatist regions that have run their own affairs with Russian support since wars in the early 1990s.

In protests that began Friday, demonstrators initially called for changes in the dates of planned elections and the electoral system. But after Mr. Saakashvili rejected their demands and accused their leaders of serving the Kremlin, they made his resignation their central aim.

In a nearly 30-minute televised address late yesterday, Mr. Saakashvili said he regretted the use of force, but argued that it was necessary to prevent the country from sliding into chaos.

“Everyone has the opportunity to express their protest in a democratic country and I, as a democrat, have always defended the right of people to protest … but the authorities will never allow destabilization and chaos in Georgia,” he said, flanked by Georgian and EU flags.

The state of emergency must be approved by parliament within two days.

The White House voiced concern over yesterday’s events.

“We urge that any protests be peaceful and that both sides refrain from violence,” a spokesman for the National Security Council, Gordon Johndroe, said. “The government and opposition should engage in a constructive dialogue with each other. We will continue to monitor the situation.”