Police fired tear gas Tuesday at several thousand demonstrators attempting to block access by lawmakers to the Parliament building in the Thai capital.

Reporters at the scene Tuesday saw at least one person injured by the gas. Sounds of gunfire were also heard but senior police officials said that only tear gas was being used against the crowd.

“I don’t think there are many injuries,” police Maj. Gen. Viboon Bangthamai said.

The protests are part of an effort by the People’s Alliance for Democracy to bring down the government, which it says is merely a proxy for ex-Prime Minister Thaksin Shinawatra, who was ousted in 2006 by military leaders who accused him of corruption and who now resides in exile.

The alliance, which is also occupying the prime minister’s residence, marshaled the protesters around streets leading to the Parliament during the night.

Police moved in and early morning fired 40 to 50 canisters of tear gas against more than 4,000 of the demonstrators.

Lawmakers were due to enter Parliament for a session later Tuesday.

Thailand has been wracked in recent months by political turmoil that has all but paralyzed the government.