Diplomatic missions in Hong Kong should perform their duties appropriately and refrain from interfering in China’s internal affairs or engaging in "destructive activities", the chief executive said.

That came when John Lee was asked, during a regular press briefing ahead of his weekly Executive Council meeting, about a reception hosted by US consul general Julie Eadah, who assumed office last month, that was attended by some opposition figures.

"Consuls have the responsibility to abide by relevant international conventions and established diplomatic practices," Lee said.

"They should perform their duties in Hong Kong in a manner befitting their diplomatic status and refrain from interfering in China's internal affairs – and Hong Kong's affairs – under any pretext or in any form.

"They should respect China's sovereignty and the rule of law in Hong Kong. I hope all consuls in Hong Kong will engage in constructive activities, not destructive activities."

Eadeh paid Beijing’s top diplomat in the SAR, Cui Jianchun, a courtesy call last week.

Cui urged Eadeh to "play a constructive role in promoting China-US relations, Hong Kong-US relations and Hong Kong's prosperity and stability", according to a statement by the Commissioner's Office of China’s Ministry of Foreign Affairs in Hong Kong.

"Ms Julie Eadeh said that she would lead the US consulate general to advance positive agendas and promote exchanges and cooperation between the US and Hong Kong," the statement added.

On a separate note, Lee vowed to pursue “for life” all absconders who fled the city, after he was asked whether SAR authorities had sought to extradite Nathan Law during his recent trip to Singapore.

Authorities in Singapore had denied entry to Nathan Law on Saturday, and he returned to San Francisco the next day.

Local newspaper Lianhe Zaobao quoted the Ministry of Home Affairs as saying that granting Law entry was "against the interests of Singapore".

"Nathan Law allegedly committed offences endangering national security. The court has issued a warrant for his arrest. He is a fugitive under the Safeguarding National Security Ordinance. The SAR government will pursue his legal liabilities for life," Lee said.

"No country should harbour criminals. Endangering national security is a serious offence and the SAR government will abide by the law and enforce it strictly, while offenders will be held accountable.

"We will use all possible means to pursue criminals for life, and will not let any fugitives go unpunished."