BANGKOK (Reuters) - Thailand's Department of Special Investigation (DSI) is being evacuated, its director said, after at least 1,000 protesters surrounded the building on Wednesday in an attempt to shut down key government buildings and ministries.

The department, Thailand's equivalent of the Federal Bureau of Investigation in the United States, is one of several state targets of demonstrators seeking to topple Prime Minister Yingluck Shinawatra's government.

Its offices form part of a complex of government departments, including those handling tax, immigration and land.

"We have ordered the evacuation of the DSI building," Mr Tharit Pengdit told Reuters. "All our employees will be out within half an hour."

The DSI recently indicted protest leader Suthep Thaugsuban for his alleged role, while serving as deputy prime minister, in the deaths of more than 90 people in a 2010 military crackdown on supporters of former Thai premier Thaksin Shinawatra, Ms Yingluck's brother.