About 700 Burmese troops invaded rebel bases in Thailand in a campaign to stamp out drug production in the Golden Triangle opium-growing area, Thai military officials said. The action followed a separate attack farther north by the Thai army on Shan rebel forces of Khun Sa, the region's top warlord, they said. Thailand, embarrassed at the flow of heroin reaching Western countries from the Golden Triangle through its territory, had Burma's permission to invade Shan bases to stamp out Khun Sa's drug empire. The Shan and other Burmese rebel groups have been accused of controlling the drug trade. The Golden Triangle stretches from eastern Burma through Thailand into Laos.