Scores of young pro-democracy activists in Hong Kong faced off with riot police Saturday after a night of scuffles and arrests over Beijing's refusal to allow genuine democratic reforms in the semiautonomous region.

Several people, including one police officer, were taken away on stretchers by medical personnel after about 150 students late Friday night forced their way into government headquarters, some scaling a tall fence. Police responded with pepper spray to push them back.

Police said 12 men and a woman, aged 16 to 35, were arrested Friday night and Saturday morning, and at least 29 protesters and officers have been injured.

The chaos came at the end of the weeklong strike by students demanding China's Communist leaders organize democratic elections in 2017.

Tension over Hong Kong's political future has risen significantly since control of the former British colony passed to China in 1997.

China's leaders have promised universal suffrage for the semiautonomous region, but last month ruled out letting the public nominate candidates, instead insisting they be screened by a committee of Beijing loyalists.

Hong Kong's young people have become vocal supporters of full democracy in recent years, fueled by anger over widening inequality.

Thousands of university and college students who had spent the week boycotting classes were joined Friday by a smaller group of high school students.

Organizers said those arrested at government headquarters included Joshua Wong, a 17-year-old leader of the activist group Scholarism, who was dragged away by four officers. Wong, a recent high school graduate, gained prominence two years ago after he organized protests that forced the Hong Kong government to back off plans to introduce a Chinese national education curriculum that some feared was a form of brainwashing.

"Our movement is peaceful and does not use aggression," said University of Hong Kong students' union president Yvonne Leung. "Students who decided to storm inside (the government complex) knew about their legal responsibility."

In a statement, the government expressed regret that protesters had stormed the complex and that there were injuries, but no further details were given.

The student protest was organized independently of Occupy Central, an alliance of pro-democracy activists that plan to blockade Hong Kong's financial district to call for genuine democratic reforms.

On Saturday, several Occupy Central members joined students protesting outside the square.

Benny Tai, a key leader of the movement, told reporters the group would "stay with the students until the end and risk getting arrested ourselves". Tai also criticized the amount of force police used on students.

Occupy Central has hinted that their blockade would begin Wednesday, China's National Day holiday, and Tai said the protest would go ahead as scheduled.