HONG Kong police have ended their blockade of a university campus after surrounding it for 12 days to try to arrest anti-government protesters holed up inside.

Police removed a stash of nearly 4000 petrol bombs left behind by protesters, who fought pitched battles about two weeks ago with riot officers on surrounding streets.

The stand-off at Hong Kong Polytechnic University was one of the most dramatic episodes in nearly six months of unrest that began in June with a huge march against an extradition Bill seen as an erosion of freedoms promised when the former British colony returned to Chinese control in 1997.

Protesters have since expanded their demands to include fully democratic elections and an investigation into police use of tear gas, rubber bullets and other force to suppress the demonstrations. Police have arrested 5890 people since June, ranging in age from 11 to 83.

About 100 officers first entered the Polytechnic campus yesterday to collect evidence and remove dangerous items. A police statement said that over two days, they seized 3989 petrol bombs, 1339 explosive items, 601 bottles of corrosive liquids and 573 weapons. No protesters were found. One masked man told media the night before police came in that about 20 people were still hiding to avoid arrest.

They were the holdouts from perhaps 1100 who had retreated inside after the battles with police. A few escaped the cordon but police say they arrested 810 people and recorded the details of 300 minors who could face charges later.

Another 567 people were arrested in the vicinity of the university.