The four Hong Kong activists who sought protection at the US consulate on Tuesday had discussed their intentions with staff from the diplomatic outpost who gave them the green light to enter the compound before “firmly” asking them to leave, a Britain-based group helping them has alleged.

Three of the activists were seeking asylum, while the fourth, who claims to be a US citizen, is accusing the consulate of neglecting its duty to help him, the Post has learned, raising more questions about a dramatic incident that could have triggered a diplomatic row to further escalate tensions between Beijing and Washington, with Hong Kong in the middle.

The allegations were made by Friends of Hong Kong, the group that was also behind a failed asylum bid by Tony Chung Hon-lam, an activist who was arrested the same day near the consulate on secession charges under the national security law.

A spokesman from the US State Department, which oversees the work of American consulates and embassies, would not respond to the allegations directly, citing instead the official line that asylum could only be granted upon the claimant’s arrival in the United States.

“Due to privacy considerations, we cannot comment on our communications with US citizens,” the spokesman said.

Chung, former convenor of the now-defunct pro-independence group Studentlocalism, was arrested by national security police at a Pacific Coffee outlet opposite the US consulate on Garden Road on Tuesday morning. His case is now in court and he has been denied bail.

Separately, the other four activists – some of whom are understood to be facing prosecution over anti-government protests– approached the consulate that afternoon and were let into the compound, as witnessed by a Post reporter, only to be turned away later.

A Friends of Hong Kong statement obtained by the Post laid out the activists’ account of events, and how they were in the premises for a short time before they were asked “very firmly” by consulate staff to leave.

The group did not identify the four, but claimed that the US citizen among them had first called the consulate’s emergency hotline and was told by staff that he was eligible for help. Along with another unidentified American citizen living in the US, he also negotiated bringing his three fellow activists to the consulate, the group said.

They were told that if they approached the consulate they would be allowed in, it said.

The US citizen, through Friends of Hong Kong, expressed outrage that the consulate would not deal with his case.

The group said it was aware that official US policy was to grant asylum only on American soil, but it cited exceptions, such as the case of Chinese dissident Chen Guangchen, who escaped house arrest in 2012 and sought refuge at the US embassy in Beijing. He was protected and allowed to fly to the US.

The group also reached out to the Foreign, Commonwealth and Development Office in Britain for help. A spokesman for the office refused to comment.

Washington’s open support for Hong Kong’s anti-government movement and its frequent offers of help to protesters, including recognising their asylum claims, has encouraged activists to approach its diplomatic mission in the city.

But political commentators and observers have noted that the US does not want to open the floodgates to asylum seekers in this manner and risk escalating tensions with the Beijing and Hong Kong governments.