Japan is watching the situation in Hong Kong "with strong concern" after demonstrators took to the streets to protest China's plan to enact a controversial security law, the top government spokesman said Monday.

Chief Cabinet Secretary Yoshihide Suga told a press conference that a free and open system ought to be maintained in Hong Kong under the "one country, two systems" framework, adding the semi-autonomous region should be allowed to thrive in "a democratic and stable manner."

"We are closely following developments regarding deliberations on the bill and protests in Hong Kong with strong concern," Suga said. "We hope that the Chinese side will address this issue in a sensible way."

Hong Kong police on Sunday used tear gas and water cannon to disperse hundreds of demonstrators decrying China's proposal of a bill that would crack down on what Beijing considers subversive activity in the former British colony, the scene of violent large-scale protests since last June.

As tensions between China and the United States heighten over a range of issues including the true origin of the coronavirus pandemic and the situation in Hong Kong, Suga said the nations must develop a stable relationship to safeguard regional and international peace and stability.

U.S. President Donald Trump has been stepping up his anti-Chinese rhetoric, warning of reacting "very strongly" to Beijing's planned national security law.

China hit back, saying a "political virus" is spreading in the United States.

"Every opportunity, this political virus is used to attack and discredit China," Chinese Foreign Minister Wang Yi said Sunday during a press conference on the sidelines of the country's annual legislative meetings.

Related coverage:

Hong Kong police fire tear gas, water cannon at protestors

China's declaring security law in Hong Kong draws global concern

Japan calls for free, open Hong Kong as China eyes security bill