KINSHASA ? An Indian businessman has gone on trial in Kinshasa accused of trying to smuggle half a million dollars' (343,000 euros') worth of diamonds out of the Democratic Republic of Congo.

Police said they stopped Ajudiya Pravin Kumar at Kinshasa airport on December 10 as he was about to return to India and found more than eight kilograms (18 pounds) of rough diamonds in a plastic bag in his luggage.

Kumar did not have a permit to export the gems and was brought before a court in the city charged with illegally possessing and trafficking diamonds, attempted corruption and fraud.

Experts from the Congolese centre for valuing and certifying minerals (CEEC) said the diamonds weighed 42,000 carats, or 8.4 kg.

Kumar, who has worked as a diamond trader in Congo for the last six years, told the court he had not realized the stones were diamonds.

"I bought stones which were to be used to make ladies' necklaces -- not diamonds," he said.

"The stones I bought at the art market (in Kinshasa) are ordinary stones, souvenirs for my family."

CEEC's technical director Amuri Dayito told the court the package contained industrial-grade diamonds rather than gems suitable for jewelry.

"Mr Kumar is a professional who is well familiar with the different standards of diamonds," Dayito said, implying that Kumar could not have confused diamonds with other stones.

A verdict in the case is expected by Thursday.