An explosion and gunfire rang out near a sprawling anti-government protest site in the Thai capital early on Tuesday after the protesters' leader warned that government supporters were planning to bring armed militants to Bangkok.
Weeks of unrest, in which protesters have barricaded several Bangkok intersections, have been interrupted by occasional bombs and gunfire, with one blast killing a woman and a young brother and sister in a shopping district on Sunday.
There was another explosion and more gunfire near one protest site on the edge of Bangkok's Lumpini Park in the early hours of Tuesday, national security chief Paradorn Pattanathabutr told Reuters.
Two men were wounded, medical sources said.
"Last night, we don't know where and who it came from, but there was an explosion and the sound of gunfire from 1 a.m.," Paradorn said. "Officials will investigate the area this morning and there should be more information soon."
He also said there was an explosion near the office of the opposition Democrat Party. No one was hurt.
The protesters, whose disruption of a general election this month left Thailand in political limbo, aim to unseat caretaker Prime Minister Yingluck Shinawatra and erase the influence of her brother, former premier Thaksin Shinawatra, who is seen by many as the power behind the government.
Protest leader Suthep Thaugsuban accused Jatuporn Promphan, a leader of the "red shirt" supporters of Thaksin, and of Yingluck's government, of wanting to bring armed militants to Bangkok from their power base in the mainly rural north and northeast, setting the stage for potential conflict.
He also accused police of doing nothing about it.
"It is clear that Jatuporn wants to divide the country in two," Suthep told supporters late on Monday.
Suthep said protesters would target Shinawatra businesses again on Tuesday, a threat that sent stock prices tumbling last week. Some shares were recovering on Tuesday.
SC Asset Corp, a property developer controlled by the Shinawatra family, lost almost 10 percent in the second half of last week and mobile handset distributor M-Link Asia Corp, also with links to the family, lost 12 percent.
SC Asset was up 2 percent at 0530 GMT and M-Link up nearly 7 percent.
National flag carrier Thai Airways International releases 2013 results on Tuesday and is expected to report a huge loss. It may cite a slump in tourism since the protests began last November as one of the factors.
Trade figures released on Tuesday showed a huge 15.5 percent drop in imports in January from a year before, reflecting weakness in consumption, construction and other activities as the political crisis deepened. Exports dropped 2 percent.
Thailand is an export base for top global car makers and a major producer of hard disk drives.
Imports were lower in most sectors, with machines and parts down 16 percent year-on-year, computers and parts down 19 percent, auto parts down 31.8 percent, steel products down 14.3 percent and consumer goods down 5.3 percent.
At least 20 people have been killed and more than 700 wounded since the protests began in November.
It is the worst political violence since 2010, when Thaksin's supporters paralyzed Bangkok for weeks. More than 90 people were killed and 2,000 wounded during that unrest, which ended when Suthep, then a deputy premier, sent in troops.
Demonstrators accuse former telecoms tycoon Thaksin of nepotism and corruption and say that, prior to being ousted by the army in 2006, he used taxpayers' money for populist policies such as a controversial subsidy for rice farmers and easy loans that bought him the loyalty of millions.
In a bit of good news for Yingluck, the Election Commission approved a 712 million baht ($21.87 million) fund to be drawn from the central budget for rice farmers, some of whom have been waiting months for payment under a state subsidy scheme.
The sum will go some way towards appeasing the farmers, who protested in Bangkok last week demanding to speak to Yingluck, but is a tiny fraction of the estimated 130 billion baht her government needs to pay to nearly a million rural workers. ($1 = 32.56 baht)
(Additional reporting by Amy Sawitta Lefevre, Aukkarapon Niyomyat and Kitiphong Thaichareon; Writing by Nick Macfie; Editing by Alan Raybould)