Hong Kong security tightened as top Chinese official visits

Beijing Hong Kong affairs responsible Zhang Dejiang arrives amid concerns over the territory's freedoms and interference by China.

Pro-democracy groups are said to stage protests during the visit, the BBC reports.

More than 6,000 police have been deployed, drones banned and tall barriers put up in central areas.

Zhang, who is also chairman of the National People's Congress Standing Committee, and so China's third-highest ranking leader, will speak at an economic conference during his three-day visit, but will also meet with a group of pro-democracy lawmakers.

Zhang is the highest ranking Chinese official to visit Hong Kong since 2014 when thousands of protesters took over major parts of the city to demand fully free elections.

Since then, a number of so-called "localist" groups have sprung up and proven willing to use violence to battle what is considered a dilution of the city's identity, fearing growing social and political influence from mainland China.

Nevertheless, pro-democracy activists are upset they will be denied the chance to get close to Zhang, and have vowed to challenge the security restriction, news sources claim.

The conflict lies in the fact that Hong Kong enjoys freedoms unseen on the mainland, which were fundamental to the handover agreement when Hong Kong was returned to China by the British in 1997. Many feel such freedoms were threatened when  with the disappearance of five Hong Kong booksellers known for publishing controversial books about Chinese leaders.

The men were later found to have been detained by mainland authorities in what the UK foreign office called a "serious breach" of protocol.