Authorities confiscated 1.3 tons of chickens found in a truck early Tuesday morning, said Nguyen Thang Loi, director of Lang Son provincial market control department. The chickens will be destroyed, he added.

In neighboring Quang Ninh province, authorities on Sunday confiscated 4.3 tons of chickens smuggled in from China in two separate cases, said provincial chief market inspector Nguyen Dang Truong.

Loi said his staff have confiscated some 50 tons of chickens smuggled in from China so far this year, while authorities in Quang Ninh have confiscated and destroyed more than 60 tons of the birds in the same period.

"We are fighting an uphill battle against smugglers who use two-way radios to deal with us," Loi said.

The H5N1 bird flu virus has hit Vietnam hard this year, ravaging poultry stocks across the country. It has killed 46 people in Vietnam since the virus began spreading in late 2003. Animal experts have blamed unvaccinated birds smuggled across borders for fanning the disease, but local officials have struggled to stop the illegal transport across Vietnam's long porous border with China.