Tens of thousands of Thai anti-government protesters rallied across Bangkok in their latest bid to topple Prime Minister Yingluck Shinawatra before today's crucial vote to elect a new Senate.
Waving flags and blowing whistles, the protesters marched from Lumpini Park in the capital's business district towards the city's old quarter.
"The rally has been largely peaceful and very disciplined. Protesters are now heading back to their base in the park after a series of symbolic ceremonies," said Paradorn Pattanathabutr, a security adviser to the prime minister.
"We expected the crowd to be around 50,000, but the number of protesters doesn't look like it will exceed 30,000," he added.
A grenade exploded as protesters passed the Foreign Ministry offices, but no one was hurt, police said. It was unclear who was responsible for the attack.
Thailand has been in crisis since former premier Thaksin Shinawatra, Yingluck's brother, was ousted in a 2006 coup.
The conflict broadly pits the Bangkok-based middle class and royalist establishment against the mostly poorer, rural supporters of the Shinawatras.
Yesterday's march was seen as a test of the anti-government movement's popularity because the number of protesters has dwindled considerably in recent weeks.
By mid-afternoon, police put the crowd at about 20,000.
About 500 protesters from the Network of Students and People for the Reform of Thailand, a splinter group of the main protest group, broke into the compound of Government House, a site largely abandoned by officials.
Protesters want political and electoral reforms before a new general election and to rid the country of Thaksin's influence.
"We will no longer accept this oppressive regime. They, Thaksin and Yingluck, are no longer welcome in Thailand," protest leader Suthep Thaugsuban said as he led protesters who shouted: "Yingluck, get out!".
Yingluck has dismissed calls by protesters to step down, but faces several legal challenges that could lead to her removal.
She has until tomorrow to defend herself before the National Anti-Corruption Commission (NACC) for dereliction of duty over a rice-buying scheme that has run up huge losses.
If the commission recommends her impeachment, she could be removed from office by the upper house Senate, which may have an anti-Thaksin majority after the election for half its members today.
The vote is to elect 77 senators for the 150-seat Senate.
The rest are appointed, and a government attempt to make it a fully elected body was one of the triggers for the latest unrest since November.
The non-elected senators are picked by judges and senior officials from agencies such as the NACC, members of an establishment seen by supporters of the government as generally anti-Thaksin.