SINGAPORE (Reuters) - Singapore should end harassment of peaceful activists, Human Rights Watch has said, after participants at a candlelight vigil for a man being executed for drug trafficking were stopped from leaving the country.

On July 13, about 10 people, including opponents of the death penalty and relatives Prabagaran Srivijayan, 22, attended the vigil outside Changi Prison in support of the man, who was to be hanged early the next morning.

The man, who was executed on July 14, was convicted of trafficking 22.4 grams of heroin into Singapore.

During the vigil, participants said they were approached by police and told that a police report had been filed and that they were to remove the candles.

The police removed the candles and photographs of Prabagaran but the participants say they were not asked to disperse.

Assemblies and processions for a cause in public places without a permit is a criminal offense in Singapore. Anyone convicted of organizing such an assembly faces penalties of up to S$10,000 ($7,440) in fines and up to six months in jail.

The Singapore government has said that the law is required to provide for the individual’s rights for political expression without compromising on “order and safety”.

Among those at the vigil were a journalist, who is an activist against capital punishment, an editor of independent online blog “Online Citizen” and a filmmaker whose most recent work focused on the detention in 1987 of political activists under Singapore’s Internal Security Act.

The three said in social media postings that they had been prevented from leaving the country, and had been told that they were required to stay in Singapore to assist police with an investigation.

As of Friday afternoon, police were not able to respond to requests by Reuters for comment.

Human Rights Watch said the government should respect the right of free speech and assembly.

“The government should end its harassment of activists campaigning against capital punishment and respect their rights to freedom of expression and peaceful assembly,” the group said in a release on Thursday.

None of the three had been arrested or charged, Kirsten Han, the activist and journalist, told Reuters.