A six-tonne shipment of smuggled ivory en route from Africa to Japan has been seized in Singapore, officials say.

The 532 elephant tusks and more than 40,000 cut pieces of ivory were found in wooden crates in a container after a tip-off.

The illegal cargo, believed to be worth $850,000, is Singapore's largest ivory seizure for more than 15 years.

No details have been revealed of the African country of origin so far, but one report said a number of arrests had been made on the continent.

Singapore is a signatory to international conventions banning trade in endangered species and prohibits the import and export of wildlife without a permit.

Traffickers face a fine of up to $5,000 and possible imprisonment.

Thriving market

The cargo was destined for Japan, where there is a thriving market for name seals or "hankos", according to Singapore's Agri-Food and Veterinary Authority (AVA) which made the discovery.

Officials had refused to confirm reports of the haul made on 28 June until now for fear of compromising an investigation, AVA spokesman Goh Shih Yong said.

A representative of a Kenyan-based international organisation fighting wildlife smuggling said several men had been arrested in Africa in connection with the seizure.

The African elephant is an endangered species protected under the Convention on International Trade in Endangered Species, but despite a worldwide ban on the ivory trade without a permit, smuggling has continued.

One study released in March found that it is often smuggled to Asian countries where it goes for an average of $250 a kilo, five times what it fetches in Africa.