Police retrieved no video footage from near the scene of Thursday's shooting and grenade attacks at Ratchadamnoen Avenue because power to their closed-circuit television (CCTV) cameras was cut.
Chana Songkhram police station deputy chief Somyos Udomraksasap said investigators had examined all the cameras in the vicinity of Thursday's attacks on anti-government People's Democratic Reform Committee (PDRC) protesters and found none were functioning. They will find and question witnesses in a bid to find some leads, he said.
Three people were killed and 22 wounded in the drive-by shooting and grenade attacks early on Thursday.
Pol Maj Gen Chanthawit Rammasoot, deputy chief of the Metropolitan Police Bureau, said security measures had been adjusted following the attacks. All checkpoints would be moved closer to all anti-government rally sites, he said.
Meanwhile, Amnesty International called on the Thai authorities to bring to justice those responsible for the attacks.
“The appalling attack is the latest escalation of political violence. Authorities must launch a thorough investigation, in accordance with Thailand’s international human rights obligations,” said Rupert Abbott, Amnesty International’s Deputy Asia Pacific Director.
“A failure to investigate the attack and hold those responsible accountable would signal that impunity rules in Thailand and risk an increasingly vicious cycle of retaliatory violence. It would also fly in the face of victims’ and their families’ right to justice" Mr Abbott said.