Sri Lankan police said they had recovered a stolen diamond worth $13,600 that was swallowed by a Chinese man at a gem exhibition after he was administered a dose of laxatives.

The 32-year-old man swallowed the 1.5-carat diamond when he was standing at a stall at Sri Lanka's annual gem and jewellery show in the capital Colombo.

"He passed the stone this afternoon... and the evidence is now with gem experts," police spokesman Ajith Rohana said, adding a judge had visited the suspect in hospital and remanded him in custody on theft charges.

The man swallowed the diamond valued at $13,600 while showing interest in buying gems from the exhibition stall. He was administered laxatives in hospital.

Police are looking for another Chinese man who fled from the exhibition after the theft was discovered.

Police said the accused had been constantly monitored by armed guards to ensure retrieval of the diamond.

The diamond's owner, Suresh de Silva, of the Belgrade International gem store, said the man had offered to pay for the 7.2mm-diameter stone, but exhibition organisers wanted to press charges.

Sri Lanka does not mine diamonds but it has a large gem and jewellery industry and is famed for its blue sapphires.