Thailand's army spokesman says more than 1,000 anti-government protesters have stormed inside the army's headquarters, the latest high-profile target in a bid to topple Prime Minister Yingluck Shinawatra.

Spokesman Col. Sansern Kaewkamnerd says the protesters broke a padlock at the gate of the compound and then pushed their way inside Friday.

He said: "They are inside the courtyard and have not entered any buildings."

The demonstrations that started Sunday have raised fears of fresh political turmoil and instability in Thailand.

They pose the biggest threat to Yingluck's administration since she came to power in 2011.

Groups of protesters were scattered around Bangkok Friday. Some are still occupying the Finance Ministry, which they stormed Monday. Others are holed up at a sprawling government office compound.