(New York) – Thai authorities should promptly and impartially investigate the alleged torture of suspects while they were held incommunicado in military custody, Human Rights Watch said today.

Four suspects in a grenade attack on the Bangkok criminal court alleged that they were tortured while being held in military custody from March 9 to 15, 2015, according to the legal defense group Thai Lawyers for Human Rights. The four – Sansern Sriounruen, Chanwit Chariyanukul, Norapat Luephon, and Wichai Yusuk – said interrogators slapped, punched, and kicked them in the head, chest, and back. They allege that they were also tortured with electrical shocks that left marks on their skin. The suspects asserted that authorities tortured them to extract information and to force them to confess to involvement in the late evening attack on March 7 in which a grenade exploded in the parking lot of the Bangkok criminal court.

“These serious allegations of torture in military detention are further cause for alarm about ongoing rights abuses under martial law in Thailand,” said Brad Adams, Asia director. “Only a prompt and impartial investigation that results in holding those responsible to account can resolve this matter.”

Human Rights Watch has repeatedly raised serious concerns regarding use of secret military detention by the ruling National Council for Peace and Order (NCPO). Since the May 2014 coup, the NCPO, headed by Prime Minister Gen. Prayuth Chan-ocha, has detained hundreds of politicians, activists, journalists, and people they accuse of supporting the deposed government, disrespecting or offending the monarchy, or being involved in anti-coup protests and activities. Military personnel have interrogated many of these detainees without providing access to their lawyers or ensuring other safeguards against mistreatment. The NCPO continually refuses to provide information about people in secret detention. The risk of enforced disappearance, torture, and other ill-treatment significantly increases when detainees are held incommunicado in military detention.

Thailand’s human rights obligations remain in place, including the prohibition of torture and other ill-treatment, which applies fully at all times, regardless of martial law or political conditions.

The International Covenant on Civil and Political Rights, to which Thailand is a party, prohibits arbitrary arrest and detention; torture and other cruel, inhuman, or degrading treatment; and extrajudicial execution. In addition, under international law and United Nations principles on the right to remedy for human rights violations, governments have the duty to investigate allegations of serious human rights violations and prosecute those responsible.

Prayuth has given repeated public assurances that detainees would be safe in military custody. On July 25, 2014, he said in a televised speech: “The NCPO would like to ask the international community to understand that we have never committed serious human rights violations. We have no policy to assault, kill, torture, rape, or harm anyone.”

However, despite this pledge, there still have been no indications of any official inquiry by Thai authorities into reports of torture and mistreatment in military custody.

“The Thai junta should immediately stop holding people in secret military detention,” Adams said. “Martial law should be revoked to end the abusive climate that has loomed over Thailand since last May’s coup.”