HONG KONG — Cambodian opposition leader Kem Sokha was released on bail Monday, a year after he was jailed on treason charges that were widely seen as politically motivated and prevented him from challenging Prime Minister Hun Sen in elections.

Kem Sokha was released from a remote jail close to the border with Vietnam around 3 a.m. Monday, according to the Phnom Penh Municipal Court, which cited his poor health. Lawyers and family members said he would be confined to a one-block radius surrounding his home and under court supervision.

Under the terms of his release, he is barred from all political activities as well as contact with his colleagues in the opposition and foreign nationals allegedly linked to his treason charges.

“He is virtually under house arrest,” said Mu Sochua, deputy leader of his now-dissolved opposition party. 

Hundreds of supporters and reporters gathered around his house in Phnom Penh on Monday morning, but Chan Chen, his lawyer, said he would not be meeting supporters or making any public statements. 

Kem Sokha was the leader of the opposition Cambodia National Rescue Party and was arrested in September on charges of working with foreign agents to overthrow Hun Sen, who has ruled Cambodia for more than three decades. A few months after his arrest, his party was dissolved, and its senior members were barred from participating in politics for five years. 

The moves were widely viewed as a way to silence critics and anyone who could pose a threat to the dominance of Hun Sen and his Cambodian People’s Party ahead of elections held in July. In those elections, Hun Sen’s party ran largely uncontested and won every available seat — cementing one-party rule in Cambodia and prompting widespread criticism from the international community. The United States and the European Union, which have long supported the growth of democracy in the Southeast Asian country as it emerged from the brutal Khmer Rouge regime, refused to send monitors to observe the vote, which they said was neither free nor fair. 

The vote extended Hun Sen’s 33-year rule for five more years. Legislators from his party took their seats this month. Hun Sen’s government insists it should be viewed as legitimately elected and as having a strong mandate from the Cambodian people. 

Since the elections, dozens of other political prisoners have been released, including journalists, opposition leaders and political commentators critical of Hun Sen’s government. But charges against Kem Sokha have not been dropped entirely, and rights activists say Cambodia has not gone far enough by releasing him conditionally. 

“There’s been no justice served here, just the temporary release of an opposition political leader that prosecutors could undo at any time,” said Phil Robertson, deputy Asia director for Human Rights Watch. 

Analysts had predicted that these critics, all jailed before the vote, would be released after Hun Sen had cemented his grip on power in a move to avoid sanctions or other punishment from the international community. In August, the United States said it would extend a visa ban imposed on top Cambodian government officials, and the European Union has mulled removing Cambodia from a preferential trade agreement under which its goods have tariff-free access to the European market. 

“Hun Sen is using a strategy of incremental appeasement, whereby small concessions aim to produce large dividends,” said Lee Morgenbesser, a lecturer at Griffith University in Australia who studies Cambodian politics and authoritarian regimes. 

He said he doubted it would be enough to assuage the European Union and the United States, which are under pressure to counter the erosion of democracy in Cambodia.

Yet Cambodia is fairly insulated from the West’s ire because it has the firm backing of regional powerhouse China, which has been tightening its control of the Southeast Asian country’s economy.

Now with Hun Sen and his party firmly ensconced for the next five years, Kem Sokha in poor health and the main opposition party banned, the release is unlikely to have much effect on the country.

“Sadly, this makes him inconsequential to the new political order,” Morgenbesser said.

San Sel in Phnom Penh, Cambodia, contributed to this report.