"The laws have been signed and they are now effective," said Mongkol na Songkhla, who became health minister after a Sept. 19 military coup. He cited the ballooning costs of treatment as the reason for the move.

"We have to do this because we have so many patients to treat with so little budget. We can’t watch our people die and their patents have been here for so long," he told Reuters.

Under World Trade Organization rules, a government is allowed to declare a "national emergency" and license the production or sale of a patented drug without the permission of the foreign patent owner.

Drug companies reacted angrily to the announcement, saying they had been kept in the dark, and urged Mongkol to reconsider a decision they said could lead to many firms leaving the country.

"No company has received any contact," said Teera Chakajnorodom, President of the Pharmaceutical Research and Manufacturers Association (PReMA), an industry umbrella group.

"It has stunned our industry."

"We’ve heard it’s not just HIV drugs, it’s also cancer drugs and cardiovascular drugs," he said. "This is very new and goes very far."

Confusion remained about what drugs were affected.

Mongkol said the drugs were HIV-AIDS and heart disease treatments but declined to confirm newspaper reports they were Abbott Laboratories’ Kaletra, and Plavix, a blockbuster anti-clotting agent sold by Sanofi-Aventis and BristolMyers Squibb.

In November, two months after the army’s removal of Prime Minister Thaksin Shinawatra, the interim government issued its first compulsory license, to make a generic version of Efavirenz, an anti-retroviral.

That decision drew a swift riposte from US drug maker and patent holder Merck & Co. Inc. By contrast, AIDS activists applauded Bangkok for taking a bold stance.