Around 150 inmates facing death sentences in Sri Lanka have started a hunger strike in a bid to suspend their verdicts after the country's president pardoned a former lawmaker involved in a murder.

The lawmaker's surprise release Thursday after he was pardoned by President Gotabhaya Rajapaksa has drawn widespread criticism, including from the Office of the United Nations High Commissioner for Human Rights (OHCHR) and the United States ambassador in Sri Lanka.

Duminda Silva is widely seen as a favorite of Sri Lanka's ruling Rajapaksa family and had been serving a death sentence over the killing of a rival lawmaker from his own party in an election-related attack about 10 years ago.

About 150 inmates sentenced to death were striking, demanding their sentences be commuted to life terms, prison spokesperson Chandana Ekanayake said Friday. He said prison officials were in discussions with the Justice Ministry and other government officials to resolve the issue but declined to provide further details.

Sri Lankan prisons are highly congested with more than 26,000 inmates crowded in facilities with a capacity of 10,000. Unrest related to COVID-19 erupted in one prison last year, and at least 11 inmates were killed and more than 100 wounded when guards opened fire to control the unrest. Silva's surprise release appeared to have set off the hunger strike.

The OHCHR said Silva's case "is another example of selective, arbitrary granting of pardons that weakens rule of law and undermines accountability."

U.S. Ambassador Alaina B. Teplitz in a tweet Thursday said the pardon of Silva "undermines rule of law."

Sri Lanka has not hanged a prisoner since 1976 even though courts routinely pass death sentences. Rajapaksa's predecessor, Maithripala Sirisena, had vowed to end the moratorium on capital punishment and to use it against those convicted of drug crimes.

Prison officials hired two executioners to carry out the hangings, but none took place during Sirisena's tenure.