BEIJING (Reuters) - Police in north-eastern China have arrested three people and are looking for a fourth who built a fake interrogation centre and pretended to be graft inspectors, kidnapping a local official and his wife to extort money, state media said.

Since President Xi Jinping began his crackdown on deep-rooted graft three years ago, there has been a series of cases of criminals passing themselves off as anti-corruption officials to get people to hand over their supposedly ill-gotten gains.

In the latest case, in the north-eastern province of Heilongjiang in August, the four suspects forced their way into the home of an agricultural official, declared they were from the prosecutors' office and led away the official and his wife with hoods over their heads, Chinese media said.

The official, named as Zhang Wei, and his wife were driven to a building in which there was a room set up to look like an interrogation room, including a government seal on the wall, media said.

"Two of them started to question me and came up with several issues of breaking the law. I said these issues simply didn't exist, and when after a few hours they'd not got any answers, they started to get nervous," Zhang said.

Finally he offered to pay up 200,000 yuan (S$43,750) and the two sides ended up settling on 400,000 yuan and let Zhang and his wife go to get the money. Zhang then called the police who arrested three of the suspects.

Police later discovered the suspects had spent 200,000 yuan and three months to get the fake interrogation room ready for their scheme.

The story was first reported on Chinese news portals on Monday (Oct 19) and more widely picked up by Chinese newspapers on Tuesday.