SHANGHAI, Mar 21 -- BEIJING police yesterday for the first time detained a buyer of a stolen bicycle since China enacted a law to crack down on bike thefts, Beijing news reported today.

Chaoyang District police patrolled around Chaoyang Park Bridge for 10 hours and then detected a man trying to sell a bicycle to another man.

The two men walked into a courtyard where the seller revealed a "brand-new" blue bicycle. The buyer paid 150 yuan (US$20) for the bicycle after a trial ride, the police said.

Several minutes later, police nabbed the buyer, surnamed Ji, and he admitted to buying the black-market bicycle. He said the seller promised him three-months of free repairs.

"I just wanted a low-priced bicycle, but I never consider whether it is illegal," Ji said. The police confirmed that the bicycle was stolen, but didn't reveal where it was taken from.

The seller, surnamed Hu, was also detained for selling stolen goods.

The Ministry of Public Security began cracking down on bicycle thefts nationwide from March to July. Anyone that buys, stores or sells stolen bikes will be punished according to the law.

People may also need to provide their identification cards when buying a bicycle in the future as state authorities are drafting a rule that may require buyers to register to purchase a bike.

The government has vowed to tighten supervision on bicycle sales and will raid illegal black-markets to stop the sale of stolen bicycles.