Philippine government workers crushed and burned more than five tonnes of smuggled elephant tusks worth an estimated $10m (£6m) in the biggest known destruction of trafficked ivory outside Africa.

The Manila government said the destruction of the stockpile, gathered from seizures since 2009, demonstrates its commitment to fighting the illegal ivory trade. It also eliminates any opportunity for corrupt officials to resell the ivory, as was the case in 2006 when the largest single shipment of 3.7 tonnes vanished from the inventory, according to an international network that tracks the illegal trade.

"Ivory is known to have disappeared from a number of government-held stockpiles worldwide, so it is vital that proper protocols are established," said Colman O Criodain from the World Wide Fund for Nature.

The US agency for international development and the Freeland Foundation anti-wildlife-trafficking group said they were assisting the Philippines in conducting DNA analysis of elephant tusks so that law enforcement agencies would have information on the origin and transit points of the smuggled ivory. It would also help to dismantle criminal syndicates responsible for poaching in Africa.

The director of the Bangkok-based foundation, Steven Galster, said: "This not only sends a message to wildlife traffickers that the Philippine government is taking firm action against the illegal ivory trade, but also takes a stand against corruption by burning their ivory stockpile so it cannot be stolen then sold into the black market."

The south-east Asian country has long been used as a transit route between the rest of the continent and Africa. Ivory can fetch up to $2,000/kg on the black market and more than $50,000 for a tusk.

The elephant trade information system, which tracks the illegal trade on behalf of the 1989 convention on international trade in endangered species, says the Philippines is among nine countries and territories identified as being most heavily implicated in the illegal trade. The others are China, Hong Kong, Kenya, Malaysia, South Africa, Tanzania, Thailand and Vietnam.

The Philippines is a transit point but is also known for its carving industry producing religious sculptures and artefacts.

Last year, National Geographic magazine featured an ivory collection allegedly belonging to a Roman Catholic priest, Monsignor Cristobal Garcia, who was suspended by the Vatican in 2012 because of a sex abuse case. Philippine police said they would question Garcia over the origin of the ivory icons.