Hong Kong police say “radicals and troublemakers” are infiltrating pro-democracy protests.
Officials have been struggling to contain a youth-led movement which is angry that candidates for the territory’s next elected leader will be pre-approved by China.
The last three weeks have seen some of the worst unrest in Hong Kong since Beijing took back control of the former British colony.
Police say they have not ruled out clearing occupied areas before talks between students take place on Tuesday.
“The occupied area in Mong Kok remains a very high risk area. Activists from radical organisations as well as troublemakers are mingling with other protesters. From time to time they plan, organise and direct various actions to provoke our officers and create chaos,” said Chief Superintendent Hui Chun-tak.
Political analyst Joseph Cheng described one strategy he said is being employed at the demonstrations.
“The protesters have been adopting a kind of guerilla warfare tactic: you may clear them in the morning when the numbers are low. But then they always come back late in the evening,” said Cheng.
Protesters don’t want what they say is a “fake” democracy. They say they won’t leave the streets until China allows open nominations for the elections.
Some analysts say the protest movement is one of the biggest challenges for Beijing since the Tiananmen Square crackdown 25 years ago.