China's leaders wince at the merest hint of support for the separation of any part of their country from the "motherland."

Gun-toting police officers and armies of secret ones ensure that few dare openly to express support for the notion in Tibet and Xinjiang, traditionally restive regions in the west of the country. China's rapid military modernization in recent years has been aimed in part at deterring Taiwan, which has never been ruled by the Communist Party, from making its de facto independence a formal one.

Imagine, then, their horror at the outcome of elections held in Hong Kong on Sept. 4. Six of the 70 people who won seats in the territory's Legislative Council, known as Legco, were people who want Hong Kong to be more independent from China.

Though their numbers are small, the emergence of such "localists" could change the way the party views the former British colony. It is no longer merely troubling for its endless calls for democracy. Now it looms as a new front in China's struggle against separatism.

Thanks to a system that China (gladly) inherited from the British, the outcome of elections to Legco is skewed in favor of pro-establishment politicians.

That is ensured by the reservation of 30 seats for "functional" constituencies, namely professions, industries and other groups whose members tend to support the government (another five seats also technically belong to such constituencies, but they allow almost every adult to vote, unlike the others, which have small electorates). It was no surprise, then, that the government's backers were able to take 40 seats, a majority that will ensure most of its bills will be passed. In the previous Legco elections in 2012 they took 43.

As the Communist Party in Beijing sees it, it is the composition of the opposing camp, not its slightly bigger size, that is a cause for much anxiety. Gone from Legco are several veterans who have been vocal critics of the party (which operates only covertly in Hong Kong). But localists have now gained seats for the first time. Not only do such people flirt with the idea of independence, but they are also more ready than old-guard democrats to engage in civil disobedience. Several were leaders of the "Umbrella movement" of 2014, which involved weeks of demonstrations and sit-ins on busy roads by student-led protesters demanding more democracy.

In the race for 35 seats in "geographical" constituencies, prodemocracy politicians took nearly 55 percent of the vote in a record turnout.

But a big share of this — nearly 20 percent of the vote — was for localists belonging to parties formed in the wake of the failed Umbrella campaign. Such groups seem to like portmanteau, or hybrid, names. One of the more radical of them, Youngspiration, now has two legislators.

Nathan Law of a party called Demosisto, who was a student leader during the Umbrella movement, has become the youngest ever to win a Legco seat. He calls himself a "23-year-old kid." In August, Law was sentenced to 120 hours of community service for inciting people to enter a fenced-off area at the start of the Umbrella protests.

Hong Kong's government, doubtless with prodding from Beijing, tried to keep supporters of independence from running. It introduced a rule requiring candidates to sign a declaration that they agree Hong Kong is an "inalienable part" of China, threatening criminal prosecution for doing so falsely. Six of the more outspoken hopefuls were thus excluded.

But some of those now elected have expressed support for independence. All have called for "self-determination," meaning the right of Hong Kong people to decide for themselves what sort of relationship they have with China. Youngspiration wants a referendum on this within five years. Its members believe it is necessary to decide as soon as possible what will happen after 2047; Hong Kong's constitution gives no guarantee that China's "one country, two systems" deal will continue beyond that date.

China's refusal to make concessions to the Umbrella protesters has fueled the growth of such groups, despite efforts by the government in Hong Kong to undermine support for them.

China's initial reaction to the results in Hong Kong has been guarded. Its media barely mentioned them. But the leadership's worries are clear. A government statement said that advocating independence for Hong Kong was "a threat to China's sovereignty and security" and would damage the prosperity and stability of Hong Kong. It expressed support for any legal action taken by Hong Kong's government to stop it.