Image copyright AFP Image caption Ken Tsang was photographed on 15 October being taken away by policemen, shortly before his alleged beating

Seven Hong Kong policemen have been arrested in connection with the beating of a pro-democracy protester.

A police statement said the officers, who had already been suspended, were detained on suspicion of "assault resulting in grievous body harm".

The incident took place on 15 October during clashes when police cleared an underpass by the Admiralty camp.

Civic Party protester Ken Tsang was filmed being led away in handcuffs and beaten for several minutes.

Local TV network TVB later aired footage of his assault, and Mr Tsang's lawyer said that the beatings had continued after he was taken to a police station.

The authorities suspended the officers and launched an investigation shortly after the clip was aired.

Image copyright Reuters Image caption A video filmed by the Apple Daily newspaper appeared to show officers beating a handcuffed protester

Image caption Images such as this one allegedly showing marks on Ken Tsang's back have caused outrage

On Wednesday, a police spokesman said they had not delayed investigations into the case, and that Mr Tsang had promised to show up to identify his assailants, but failed to do so.

The spokesman called on Mr Tsang to "assist the police in investigations as soon as possible".

The police also rejected previous criticism of their handling of the case, saying that their investigations had consistently followed the procedures for complaints against police officers.

"If any other officer is suspected of illegal behaviour, the police will investigate impartially and not show favouritism," said the spokesman.

Media playback is unsupported on your device Media caption The clearance operation continued on Wednesday as bailiffs, backed by police, began removing barricades

Wednesday's announcement came after police cleared one of the key protest sites at Mong Kok.

More than 140 people were arrested, including two leading student activists, Joshua Wong and Lester Shum.

Analysis: John Sudworth, BBC News, Shanghai

There have been attempts to clear Hong Kong's streets before, notably of course, right at the beginning of the protests. Video footage of the protesters defending themselves with umbrellas from the pepper spray became the defining image and only served to give the movement massive momentum.

Now though, the authorities are taking a more careful approach. Recent clearance efforts, including those over the past two days in the Mong Kok district, have been to enforce the court injunctions, won by businesses including the city's taxi drivers, angered over the effect on their businesses.

They also come at a time when the protesters are weary after two solid months of sit-ins, their numbers dwindling, and not long after the world spotlight has left China following the Apec Summit. Scenes of Hong Kong chaos might not have played well with the world leaders meeting in Beijing.

But with Mong Kok cleared, two other sites remain, including the main protest site in the heart of the financial district. Further court injunctions or not, that remains a much tougher proposition.

Dozens arrested in Hong Kong crackdown

Image copyright EPA Image caption Police formed a human barrier (top) as they moved in on the Nathan Road protest site on Wednesday