BISHKEK, Kyrgyzstan — Thousands of protesters furious over corruption and spiraling utility bills seized internal security headquarters, a state TV channel and other levers of power in Kyrgyzstan on Wednesday after government forces fatally shot dozens of demonstrators and wounded hundreds.

A revolution in the Central Asian nation was proclaimed by leaders of the opposition, who have called for the closure of a U.S. air base outside the capital that serves as a key transit point for supplies essential to the war in nearby Afghanistan.

The U.S. State Department said transport operations at the Manas base were “functioning normally.”

This mountainous former Soviet republic erupted when protesters called onto the streets by opposition parties for a day of protest began storming government buildings in the capital, Bishkek, and clashed with police. Groups of elite officers opened fire.

The Health Ministry said 40 people had died and more than 400 were wounded. Opposition activist Toktoim Umetalieva said at least 100 people had died after police opened fire with live ammunition.

Crowds of demonstrators took control of the state TV building and looted it, then marched toward the Interior Ministry, according to Associated Press reporters on the scene, before changing direction and attacking a national security building nearby. They were repelled by forces loyal to President Kurmanbek Bakiyev, whose whereabouts were a mystery.

The opposition and its supporters appeared to gain the upper hand after nightfall, and an Associated Press reporter saw opposition leader Keneshbek Duishebayev sitting in the office of the chief of the National Security Agency, Kyrgyzstan’s successor to the Soviet KGB. Duishebayev issued orders on the phone to people he said were security agents. He also gave orders to a uniformed special forces commando.

He told the AP that “we have created units to restore order” on the streets. He said Bakiyev may have fled to Osh, where he has a home.

Since coming to power in 2005 on a wave of street protests known as the Tulip Revolution, Bakiyev had ensured a measure of stability, but many observers say he has done so at the expense of democratic standards while enriching himself.