Indian customs officials last week arrested an Indian national after finding dozens of snakes and several turtles in their luggage.

Among them were several spider-tailed horned vipers, a venomous species only described by scientists in 2006 and classed as "near-threatened" by the International Union for the Conservation of Nature.

The reptiles are among over 7,000 animals, dead and alive, that have been seized along the Thailand-India air route in the last 3.5 years, said Traffic, which battles the smuggling of wild animals and plants.

"The almost-weekly discoveries and diversity of wildlife en route to India is very troubling," said Traffic's Southeast Asia director Kanitha Krishnasamy.

Many of those captured were alive, which "shows that the clamour for exotic pets is driving the trade", she added.

The group said its analysis showed that while most cases involve animals smuggled out of Thailand, over 80 percent of interceptions happened in India.

More than a third of the wildlife seized is covered by rules banning or strictly regulating their trade across international borders, Traffic added.

The group said the "scale and frequency" of the cases suggested more work was needed to investigate "the criminal networks supplying this seemingly endless conveyor belt of wildlife-stuffed bags".

They also urged Thailand to work with regional neighbours that have seen similar trafficking routes to India.

Thailand is considered a major transit hub for wildlife smugglers, who often sell highly-prized endangered creatures on the lucrative black market in China, Vietnam and Taiwan.

Last month, Thai police arrested a man suspected of smuggling two baby orangutans into the kingdom for sale.