Thailand's Election Commission has urged the government to delay the polls scheduled for February after violent clashes between riot police and protesters who wanted to stop election preparations and force Prime Minister Yingluck Shinawatra to resign.
Thai police said that one officer was killed during the clashes.
The announcement on Thursday came as fighting erupted outside a sports stadium where candidates were gathering to draw lots for their position on polling papers, according to an Associated Press reporter at the scene.
"We cannot organise free and fair elections under the constitution in the current circumstances," Election Commission member Prawit Rattanapien said at a news conference.
The demonstrators, some armed with sling shots, threw rocks and attempted to break through police lines prompting the police to use rubber bullets, tear gas and water cannon.
At least 48 people were injured.
Police Colonel Anucha Romyanan said at a press conference that three officers were wounded.
Inside the stadium, candidates for at least 27 parties took part in the lot-drawing process, which was apparently unaffected by the fighting outside the gates.
However, some election officials later left the stadium by helicopter to avoid the unrest and because protesters were blocking the exits.
Protesters were on the way to the Prime Minister's residence to continue their demonstration.
About 500 policemen have been deployed outside her house.
The clashes are the first violent incident in almost two weeks of daily demonstrations on the streets of Bangkok.
Protesters want the Prime Minister to step down and they oppose the elections, due to take place on February 2, because Yingluck is seen as sure to win them.
Her brother is the former Prime Minister Thaksin Shinawatra, who was ousted in a military coup in 2006 and lives in self-imposed exile to avoid imprisonment on corruption charges.
He or his allies have won every election for the last 12 years.
In mid-October Yingluck tried to introduce an amnesty law that would have allowed Thaksin to return as a free man, a move that sparked the latest round of protests.
On Wednesday, protesters rejected a compromise from Yingluck, who announced a proposal for a national reform council. They are planning more civil disobedience and street protests to force her to resign as caretaker Prime Minister.
Police have not tried to arrest the ringleader, Suthep Thaugsuban, who is demanding the country be led by an unelected council until reforms can be implemented.