BANGKOK - Gunmen killed an antigovernment activist and wounded two others Saturday in an attack near a protest camp in Thailand's capital, while protesters elsewhere blocked candidates from registering for elections, deepening a political crisis that threatens to derail democracy in the Southeast Asian nation.

Registration for the Feb. 2 polls was suspended in four of the country's 76 provinces, all four in the south, where the demonstrators, who are seeking to oust Prime Minister Yingluck Shinawatra, enjoy support.

The events followed comments Friday by the powerful army chief in which he declined to rule out the possibility of a coup in the country, which is a major U.S. ally, Southeast Asia's second-largest economy, and a popular tourist destination.

The long-running dispute between Thailand's bitterly divided political factions flared anew in November after Yingluck's elected government tried to introduce an amnesty bill for her brother, former Prime Minister Thaksin Shinawatra, to enable him to return to Thailand from self-imposed exile and escape a jail term for corruption.

Yingluck called early elections as a way of defusing the crisis, but the protesters are demanding she resign and hand over power to an unelected council to carry out reforms. They are trying to disrupt the polls, which most people believe will give her a strong mandate thanks to strong support in the north and northeast of the country.

On Thursday, protesters tried to overrun a Bangkok sports stadium where election candidates were gathering to draw lots for their positions on ballots. Two people, one of them a police officer, were shot dead.

The attack early Saturday took place close to a protest camp in central Bangkok, according to a government-run medical center. It said a 31-year-old man was killed by gunfire and two others were wounded in the attack, which occurred about 3:30 a.m. Local media said unidentified gunmen opened fire on guards close to a protest camp, then escaped into the night.

Hundreds of candidates Saturday were registering for the polls, but the process was stopped in four southern provinces because protesters blocked the venues and local election officials wanted to avoid violence, said Puchong Nutrawong, secretary-general of Thailand's election commission. Registration continued in a fifth province - Surat Thani - despite protests there, he said. "Our policy is to avoid any confrontation," Puchong said.

Thailand's army has stayed out of the crisis, but it has staged 11 successful coups in the country's history - the last against then-Prime Minister Thaksin in 2006 - so its intentions are being watched carefully.

Asked on Friday whether a military takeover was possible, Gen. Prayuth Chan-ocha, the army chief, said, "That door is neither open nor closed . . . it will be determined by the situation." His words were taken by some as warning that the military might one day intervene.