Police in Hong Kong on Wednesday said they issued their first arrest under the newly passed security law that critics say undermines the semi-autonomous territory’s judicial independence and gives China unprecedented power over the city.

The man was arrested for carrying a flag that called for Hong Kong’s independence, the Associated Press reported. He was reportedly intercepted by law enforcement after a crowd at the city’s Causeway Bay was issued warnings that they could be in violation of the new law. Hong Kong Police also tweeted news of the arrest.

City police said that they raised a “new purple warning flag” to warn protesters that by chanting independence slogans “they may have breached” the new law.

China passed the law on Tuesday that many in the Hong Kong media say will allow Beijing to crack down on any activity there that authorities deem subversive with secessionist aims.

Police later announced that a second person was arrested for allegedly being in violation of the new law. Dozens of other protesters have been arrested for other violations, including unlawful assembly.

Hong Kong's annual Democracy march was banned for the first time this year since the British handed rule back in 1997. Authorities cited the coronavirus for cancelling the march.

Violaters of the anti-protest law could face up to life in prison and suspects may be tried on the mainland, according to BBC News. 

Non-residents are also subject to the new law.

U.S. Secretary of State Mike Pompeo spoke out against China’s power grab in a statement shortly before reports of the bill's approval.

“If China wants to regain the trust of Hong Kongers and the international community, it should honor the promises it made to the Hong Kong people and to the United Kingdom in the U.N.-registered 1984 Sino-British Joint Declaration,” Pompeo’s statement read.

Bloomberg reported that earlier in the day, Chinese officials described the new law as a “sword of Damocles” hanging over the heads of Beijing’s top critics in the city.

In a rebuke to mainland China, Taiwan opened a migration office Wednesday for Hong Kong residents wanting to move to the island in the wake of the new law.

Taiwan is a democracy with its own government, but China claims it as a territory belonging to the mainland.

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The establishment of the office is “not only a statement on Taiwan’s support to Hong Kong’s democracy and freedom, but also highlights our determination to care for Hong Kong people,” Chen Ming-tong, Taiwan's Mainland Affairs Council minister, told reporters.

The Associated Press contributed to this report