Hong Kong institutions, including universities, need to be very sensitive to infiltration by external forces, Chief Executive Carrie Lam Cheng Yuet-ngor said on Tuesday.

Lam was responding to a question by China Daily on an international sociology study that paid 849 students from the Hong Kong University of Science and Technology to participate in a protest in 2017. The study has been published in the June issue of the American Economic Review.

The universities in Hong Kong were reminded by the city's leader of their duties to prevent the impact on local students of international academic activities with prejudice and bias.

Speaking to media on Tuesday morning ahead of the weekly Executive Council, Lam said "These external forces are at work. And how are they acting, penetrating into various institutions in Hong Kong including the universities is something that everyone in position should be very sensitive to."

"As a matter of principle that based on the events that we have seen in the latter half of 2019 until the enactment and implementation of the National Security Law (for Hong Kong), I hope there is now no doubt in the minds of many people that there are external forces quite active in Hong Kong for their ulterior motive," she said.

She urged the university management, the council chairman, and the president to be extremely careful and to make sure that university students will not be easily indoctrinated by those prejudices and bias, let alone take part in activities that will breach the laws of Hong Kong.

Lam also took the opportunity to welcome and support a draft law on countering foreign sanctions submitted to the Standing Committee of the National People's Congress - China's top legislature - on Monday for second reading.

As someone being targeted by US sanctions, Lam echoed the Chinese government's strong condemnation of these hegemonistic acts.

"Every Chinese who upholds the country's sovereignty and core interests should take the stance of strong indignation," she said.

This year, July 1 marks the 24th anniversary of Hong Kong's return to the motherland, and the centenary of the Communist Party of China.

Lam revealed that many celebrations are expected to be held to mark this special occasion in the city.

She has been invited to attend a seminar on Saturday on the relationship between the Communist Party of China and the "one country two systems" and an exhibition on the achievements of the party over the last century.