Story highlights Ruling comes after protests on Sunday

Beijing uses rarely invoked power

Hong Kong (CNN) China has barred two recently elected lawmakers from taking office in Hong Kong's legislature in an explosive ruling likely to fan fears about Beijing's growing influence over the city.

Critics -- including protesters who poured onto the city's streets Sunday -- say the decision undermines Hong Kong's own legal system and further erodes promises of autonomy made before the former British colony was returned to China in 1997.

The two lawmakers, Sixtus "Baggio" Leung and Yau Wai-ching, had their oaths of allegiance rejected after inserting curse words and waving a flag bearing the words "Hong Kong is not China."

.@Youngspiration Yau Wai-ching refers to "People's Re-fu*king of Chee-na" at oath taking https://t.co/b6dmrmfxFP — Hong Kong Free Press (@HongKongFP) October 12, 2016

China's top ruling body, invoking a rarely used power, said Monday that anyone who refuses to read the oath should be disqualified from holding office.

"Reading the vows in any dishonest, ungraceful manner is also a refusal to the oath, and it shall be void," the ruling said, according to state news agency Xinhua.

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