A leading human rights watchdog yesterday accused Thailand's army chief of trying to intimidate investigators investigating the military's role in a deadly crackdown on opposition street protests in 2010. New York-based Human Rights Watch also criticised Commander-in-Chief Prayut Chan-O-Cha for suing a lawyer of ousted premier Thaksin Shinawatra for accusing the army of killing "Red Shirt" protesters. Calling on the government to rein in Prayut, HRW said he had pressured the Justice Ministry's Department of Special Investigation over its probe into the deaths of more than 90 people, mostly civilians, in the 2010 unrest. The DSI, the kingdom's highest criminal investigation body, has so far ordered inquests into the deaths of 19 of the victims, and said it wants to question soldiers in connection with the military operation. "Abuses by soldiers took place in full view of the Thai public and the world's media, yet the Thai army chief is now trying to intimidate investigators and critics into silence," said HRW's Asia director Brad Adams. "Instead of going after his critics, he should be ensuring accountability within his ranks." There have been no prosecutions over the killings despite an election pledge by current Prime Minister Yingluck Shinawatra - Thaksin's sister - to seek justice for victims. The human rights body's own investigation concluded that the military used "excessive and unnecessary lethal force" in the crackdown. Prayut denies army abuses and has filed a defamation case against Thaksin's lawyer Robert Amsterdam for accusing the military of killing civilians in a speech in May.