KHARTOUM, July 17 (Xinhua) -- The U.S. signing of the so-called "Hong Kong Autonomy Act" into law is "a grave violation of international law" and a flagrant interference in China's internal affairs, a Sudanese political analyst said Friday.

"The United States has got used to unilateral actions that constitute a grave violation of international law," Abdul-Raziq Ziyada told Xinhua.

"The American move also represents interference in China's internal affairs as Hong Kong is an integral part of China," he added.

Ziyada underscored China's sovereign rights to adopt what it deems suitable measures to confront the U.S. move.

"China is a sovereign state and of its duty to protect its authority in Hong Kong together with the interests of its citizens against any external interference aiming at undermining the stability of the region," Ziyada said.

China has strongly condemned the U.S. move.

"The Chinese government firmly opposes and strongly condemns this move by the United States," China's Foreign Ministry said in a statement released on Wednesday.

"The Act maliciously denigrates the national security legislation for Hong Kong, and threatens to impose sanctions on China. It seriously violates international law and the basic norms underpinning international relations. It constitutes gross interference in Hong Kong affairs and China's internal affairs," the statement added.

The government of China's Hong Kong Special Administrative Region (HKSAR), for its part, expressed its strong opposition to the U.S. move and vowed to fully support the central government to adopt countermeasures.

"The U.S. move seriously violates international law and the basic norms underpinning international relations and constitutes gross interference in Hong Kong affairs and China's internal affairs," a spokesman of the HKSAR government said Wednesday.