The bellicose comments by the Liaison Office, which represents China's government in the semi-autonomous city, dramatically heighten the risk of prosecution for opposition parties and leading figures.
More than 600,000 Hong Kongers turned out over the weekend to choose candidates for upcoming legislative elections despite warnings from government officials that the exercise could breach Beijing's sweeping new law.
Polls for the city's partially elected legislature are due to take place in September.
Pro-democracy parties are keen to use seething public anger towards Beijing's increasingly authoritarian rule to win a majority within a chamber that has always been weighted in favour of pro-establishment parties.
Control could give them a greater ability to stall budgets and legislation, one of the few tactics left open to the opposition camp.
But in a statement released late Monday, the Liaison Office described the primaries as "a serious provocation against the current election system".
It said campaigning that pushed to take control of and paralyse the chamber is a breach of Article 22 of the security law.
Article 22 targets "subverting state power". It outlaws "serious interference and obstruction" of the central and Hong Kong governments, or any act that causes them to be "unable to perform their functions normally".
The Liaison Office's statement also singled out Benny Tai, a prominent democracy activist who played a leading role in organising the primary.
"The goal of the Benny Tai gang and the opposition camp is to seize power to govern Hong Kong, with a vain attempt to launch a Hong Kong version of a 'colour revolution'," the office said.
Colour revolution is a term used to describe multiple popular protest movements around the world that either swept a government from power or tried to.
However in authoritarian Communist China -- itself a state built from revolution -- the term has frequently been used by both the government and state media to describe an illegitimate revolution backed by hidden, usually western, forces.
Tai, a law professor, has previously been jailed for his involvement in peaceful pro-democracy protests in 2014.
On Tuesday, the Apple Daily newspaper published a column by Tai in which he hailed the primaries.
"Threats from the powerful did not deter tens of thousands of citizens from coming out and casting a ballot," he wrote.
"They have not given up on their determination to pursue democracy and universal suffrage."
Apple Daily is owned by Jimmy Lai, one of the few tycoons in Hong Kong to openly support democracy. He is also being prosecuted for taking part in pro-democracy protests.