At least six people have been injured in Bangkok after a grenade was thrown at cars driving past a protest camp.
Shrapnel from the blast damaged three vehicles.
Thai police said the grenade was hurled from a bridge close to the Ratchaprason intersection where anti-government protesters have been camping out for months.
Demonstraters have blocked key Bangkok intersections with tents, tyres and sandbags. They want to suspend what they say is a fragile democracy.
Protesters claim Prime Minster Yingluck Shinawatra is being controlled by her billion brother, Thaksin, toppled from power in 2006.
This week they targeted businesses linked, or once linked, to the Shinawatra family, sending stock prices tumbling.
Meanwhile Thailand’s anti-corruption body announced it was filing charges against Yingluck Shinawatra over a state-sponsored rice subsidy scheme that is near to collapse.
Farmers blockaded Yingluck’s temporary office during the week demanding payment for their crops.
Further protests are planned for Sunday.