Updated

A suspect has been arrested in the bombing of an army hospital in Bangkok that wounded 21 people, Thailand's military government announced Thursday.

Deputy Prime Minister Prawit Wongsuwan said the arrested man had been interrogated and confessed to the attack on Phramongkutklao Hospital on May 22, the third anniversary of a military coup that ousted a democratically elected government.

A high-ranking Thai security official, speaking on condition of anonymity because he was not authorized to release information, said the suspect arrested Thursday morning is a 62-year-old electrical engineer. No other details about his identity were available.

He said security camera video led to his identification, showing that the man had entered the crime scene with a cloth bag and what looked like a flower vase. The man left the room 10 minutes later without the items, he said.

A subsequent raid on his home found four pipe bombs and bomb-making materials similar to that used in the attack on the hospital, he said.

"It is considered a good thing that we are able to capture the assailant responsible for causing chaos and multiple injuries," said Prawit, who is also defense minister. He said the suspect "has confessed that he was the one that did it."

The timing of the bombing suggested strongly that it was a political act. Army chief Gen. Chalermchai Sittisart said after the blast that it appeared the explosion and two earlier blasts in Bangkok used similar explosive materials and were likely part of an attempt to disrupt the government.

"All of this was conducted with the goal of creating disorder to the administrative work of the government and NCPO," he said, referring to the National Council for Peace and Order, the official name of the junta. He cautioned that it was too early to make a judgment, however.

Publicly expressed opposition to the military government is rare, but political passions run deep in Thailand after a decade of polarization that pitted contending forces in sometimes violent conflict.

The junta has come under criticism for repeatedly putting off elections to restore civilian government. Critics suggest that the bombing could have been part of an effort to manufacture an excuse for continued military rule, or a result of infighting in the army.