BANGKOK (AP) - More than 20 people were wounded in Thailand's capital Friday when an explosion hit anti-government demonstrators marching through the capital, the city's emergency services center said.
The movement's leader, Suthep Thaugsuban, was in the procession but was not wounded in the blast, protest spokesman Akanat Promphan said.
Akanat said an explosive device was thrown into a truck driven by demonstrators that was several dozen meters (yards) ahead of Suthep.
Thailand has been wracked by repeated bouts of unrest since the military ousted former premier Thaksin Shinawatra in 2006 amid charges of corruption and alleged disrespect for the monarchy. The crisis boiled over again late last year after a failed ruling party bid to push through an amnesty bill that would have allowed Thaksin to return from exile.
Anti-government demonstrators who are now seeking to oust Thaksin's sister, Prime Minister Yingluck Shinawatra, have taken over seven key roads and overpasses in Bangkok this week, blocking them off with sandbag walls and steel barricades.
The protests have been peaceful, but small acts of violence have reported nightly at protest venues, which have been targeted in shooting attacks and with small explosives hurled at the homes of top protest supporters.
Overnight, two motorcycle-riding suspects drove past the residence of Bangkok Gov. Sukhumbhand Paribatra and hurled a grenade inside, according to Police Col. Samarn Rodkamnerd.
Sukhumbhand - who is member of the Democrat Party which is backing the protesters - was not home at the time and no injuries or serious damage was reported.
The attack was similar to another grenade attack on the home of Abhisit Vejjajiva, a former Democrat premier whose party lost to Yingluck's in a 2011 vote.
The violence comes as Yingluck faced fresh legal troubles Friday after the country's anti-corruption commission announced it would investigate her handling of a controversial rice policy.
The legal threat added to the intense pressure against her caretaker administration to resign as protesters calling for her ouster march across the capital for a fifth day to protest at government offices.
The National Anti-Corruption Commission said Thursday that it had found grounds to investigate allegations that Prime Minister Yingluck Shinawatra was criminally negligent in her handling of what the government has described as a deal to export surplus rice to China. The commission has already determined that there are grounds to press charges against her former commerce minister and more than a dozen other officials.
If found guilty, Yingluck Shinawatra would be forced to resign.