The Hong Kong government blasted the vandalism of its trade office in London as a “nefarious” act by foreign forces, an act of rebellion that came as UK and Chinese officials prepared for talks to mend ties.

“Offenders, under the cover of darkness, sprayed indecent and offensive language on the entrance of the London ETO and defiled the regional emblem of” Hong Kong, a spokesperson for the government said in a statement Wednesday, using an acronym to refer to its Economic and Trade Office.

A photo of the building in question, published by the South China Morning Post, showed red paint and writing around its entrance, although it was unclear from the image exactly what it said.

The incident took place on the eve of British Foreign Secretary James Cleverly’s arrival in Beijing to meet Chinese officials, in a bid to put the UK’s ties with China on a more even keel. Relations between the two nations have soured in recent years, in part over China’s crackdown on democracy activists in Hong Kong and Britain’s resulting offer of visas for Hong Kongers.

Representatives from the Hong Kong government and the British Consulate in Hong Kong didn’t immediately respond to requests for comment.

The Hong Kong authorities said the vandalism was a sign overseas actors were trying to cause “cause chaos and disruption in Hong Kong,” and vowed legal recourse. The city’s Secretary for Commerce and Economic Development has expressed his “deep concern” to the British Consul General in Hong Kong, the statement added.

Hong Kong has previously pursued democracy activists overseas. Last month, the city placed HK$1,000,000 ($127,650) bounties on the heads of eight democracy activists living abroad. While the city’s security law asserts global jurisdiction, most suspects wanted under the legislation that carries a maximum sentence of life in prison would not return to Hong Kong, making their prospect of arrest close to zero.