A bomb exploded at a military-run hospital in Bangkok on Monday, injuring 25 people on the third anniversary of a military coup, Thai authorities said.
Investigators found remnants of batteries and wires at the scene of the blast on the ground floor of Phramongkutklao Hospital, said deputy national police chief Srivara Ransibrahmanakul.
"We can confirm at this stage that it is a bomb," he said.
Three people suffered serious shrapnel injuries to the face and neck, but most of the victims had minor wounds, said Sansern Kaewkumnerd, a government spokesman.
It was not immediately clear who was behind the explosion or if it was connected to the anniversary of the 2014 military coup which overthrew a democratically elected government.
"Please don't connect this with any other incidents because they may or may not be connected," Mr Sansern said. "We have to wait for officials to investigate details from surveillance cameras in the area."
Phramongkutklao is a military-run hospital that is also open to civilians. The blast radius from the explosion was up to 9ft (3m), police said.