Image copyright AFP Image caption The beating of Ken Tsang led to accusations of police brutality

Seven Hong Kong police officers have been charged with allegedly attacking a demonstrator during pro-democracy protests in the territory last year.

Activist Ken Tsang was filmed being led away in handcuffs and beaten by police for several minutes on 15 October 2014.

On Thursday, Mr Tsang was told he would also be charged for assault and resisting arrest - charges he described as "groundless".

The case attracted widespread criticism of the normally respected police force.

Last year's incident took place during mass pro-democracy demonstrations and sit-ins that drew tens of thousands at their peak and paralysed Hong Kong's streets for more than two months.

The grainy footage of a group of plainclothes officers assaulting an unarmed protester was one of the most shocking images to emerge from the demonstrations, the BBC's Juliana Liu in Hong Kong reports.

The beating led to accusations of police brutality and tarnished the image of law enforcement in Hong Kong, our correspondent adds.

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

The authorities suspended the officers and launched an investigation shortly after the footage was aired on local media.

However, the police have been criticised for not naming or charging the officials until now.

On Thursday, Mr Tsang's lawyer told the BBC that the Civic Party activist now faced one count of assault and four counts of resisting arrest.

Mr Tsang told reporters the charges had not been mentioned to him before and were "ridiculous and against the facts".

"All this should not be happening one year later... I feel that the government is just trying to make a stand by arresting me," he said.

However, the chairman of the Junior Police Officers Association said the "police and the Department of Justice have been transparent in their work and always follow established procedures".

"It's just that their work has arrived at this stage now," chairman Joe Chan said, in quotes carried by the South China Morning Post.