Anti-government protesters marched defiantly through Thailand's capital on Saturday, with one group entering a police compound, undeterred by a grenade explosion the day before that wounded 35 demonstrators and killed one.
Friday's blast sent tension rippling through Bangkok after several days of relative calm that had suggested the movement to close down the government and force the resignation of Prime Minister Yingluck Shinawatra was running out of steam.
Reuters reports it was not clear who was behind the attack on the protesters. Their firebrand leader, Suthep Thaugsuban, blamed the government and said the incident would not dent the morale of thousands who this week stepped up a two-month agitation, blockading key arteries of the city and occupying ministries.
The incident, which comes just two weeks before a general election, heightens the risk of a move by the country's army to end an impasse that is starting to damage the economy.
The turmoil is the latest episode in an eight-year conflict pitting Bangkok's middle class and royalist establishment against poorer, mainly rural supporters of Yingluck and her brother, the self-exiled former premier Thaksin Shinawatra.
The protesters accuse the pair of corruption, and want Yingluck to step down to make way for an unelected "people's council" to push through broad political reforms.
Strong support from rural voters has enabled Thaksin or his allies to win every election since 2001 and Yingluck's Puea Thai Party seems certain to win the vote set for 2 February. But the protesters and opposition parties are boycotting the poll and want the prime minister to step down immediately.