PHNOM PENH, Cambodia — Fourteen Cambodian opposition activists were freed Tuesday from long prison terms, their pardons coming as the latest in a series of releases engineered by Prime Minister Hun Sen after his party's election sweep last month.

The 14 former members of the now-disbanded opposition Cambodia National Rescue Party were convicted of insurrection in connection with a street protest four years ago that turned violent. By many accounts, the violence was started by pro-government agitators, and the arrests of the opposition members were seen as political persecution.

Those freed Tuesday were serving prison terms ranging from seven to 20 years, the longer sentences given to those seen as leaders of the July 15, 2014, protest in Phnom Penh. It had been held as opposition lawmakers were boycotting parliament to demand political reforms, saying the previous year's election had been rigged by Hun Sen's ruling Cambodian People's Party.

Tuesday's releases came at about 1 a.m., a move that seemed intended to keep supporters from gathering publicly to welcome them. A court spokesman said the pardons were signed Monday by King Norodom Sihamoni at the request of Hun Sen.

At least eight other people held on political charges have been freed with pardons or on bail since the beginning of last week.

The acts of clemency came after the July 29 general election, in which Hun Sen's Cambodian People's Party won all 125 National Assembly seats. The polls were heavily criticized inside and outside Cambodia as unfair, because pro-government courts last year dissolved the Cambodian National Rescue Party, the only credible opposition grouping.

In the run-up to the election, there was a crackdown on Hun Sen's political foes and the media that crippled the opposition. Hun Sen, who has been in office since 1985, has a record of cracking down harshly when facing a serious challenge, then easing up when he no longer feels threatened.

A repentant appeal for pardons issued Friday by the 14, along with a conciliatory statement calling for national unity from the most prominent prisoner, former opposition spokesman Meach Sovannara, after his release, suggested that the latest release was carefully orchestrated by the government. Early last week, Hun Sen hinted broadly that they would be released soon.

There has been a major exception to the latest releases. Last week, the former leader of the opposition party, Kem Sokha, was denied his request to be released on bail. He has been in prison awaiting trial since last November, when he was arrested on the charge of treason for allegedly plotting with U.S. backing to overthrow the government. The charge is regarded more as politically motivated than based on fact.

Am Sam Ath, a member of the Cambodian human rights group Licadho, said there may be another opportunity on Thursday for Kem Sokha to gain his freedom, when a closed-door hearing will be held at his prison in eastern Cambodia to determine whether to renew his pre-trial detention period.