The United States on Tuesday urged all sides in Thailand to show restraint and refrain from violence as the US ally imposed emergency rule to tackle mass protests.
Washington condemned violence and called for an investigation into incidents including grenade attacks that killed one person and injured dozens more.
"We urge all sides to refrain from violence, exercise restraint, and respect the rule of law," State Department spokeswoman Marie Harf said in a statement.
"We encourage all involved to commit to sincere dialogue to resolve political differences peacefully and democratically."
Prime Minister Yingluck Shinawatra's government declared a 60-day state of emergency, which includes a ban on gatherings of more than five people, but ruled out the use of force or giving the army the leading role.
In 2010, a military-led crackdown on protests -- then led by forces sympathetic to the Shinawatra clan -- led to dozens of deaths.
Yingluck has called an election for February 2 but the main opposition party is boycotting the vote. Protesters have vowed to shut down Bangkok until Yingluck falls.
Thailand is the oldest US ally in Asia, with the kingdom then known as Siam famously offering president Abraham Lincoln elephants to fight the civil war.