Secretary for Security Chris Tang said resolute law enforcement action will be taken against illegal acts to allow the upcoming Legislative Council elections to be held in a safe and orderly manner.

He said it could be illegal for people to encourage others to cast a blank ballot or not to vote in the December 7 election.

Tang also said it is against the law for anyone to collude with foreign forces to control, or interfere in, the elections.

"We will carry out all kinds of law enforcement actions, including intelligence gathering, against any illegal act that aims to undermine the safety of the elections," he said.

"Our intelligence gathering will not stop. Nobody should think that we will not be able to track you down if you carry out illegal acts online. Such acts are no different from those carried out physically.

"If you break the law, we will be able to look for evidence, find out who you are, and arrest and prosecute you."

Speaking after Tuesday's Fight Crime Committee meeting, he said 66,585 crimes were committed in the first nine months of the year, a drop of 4.9 percent from a year ago.

While declines were registered for a majority of crimes, the number of cases relating to serious drug offences rose 9.6 percent to 935.

The number of cases involving etomidate, meanwhile, stood at 749.

As for illegal employment, Tang said about 130 suspected illegal workers and 46 employers or suspected aiders and abettors had been arrested since an inter-departmental task force was set up in September to tackle the issue.