HONG KONG — The two Hong Kong protesters were dressed head to toe in black, their faces covered in masks. They smashed their Molotov cocktails into the lobby of a public housing estate, and flames and smoke began spewing out.

This was no scene from the protest violence last year over Beijing’s dominance of Hong Kong’s affairs. This was on Sunday, and the firebombing was incited by anger over the coronavirus that originated in Wuhan, China — and plans by the Hong Kong government to use the unoccupied housing block as a quarantine area.

Angst and anger fueled by the coronavirus outbreak, which has killed more than 130 people on the mainland and has eight confirmed cases in Hong Kong, are compounding the bitterness from months of protests against Chief Executive Carrie Lam’s leadership. And it has set her government scrambling.

On Tuesday, she relented after days of heavy pressure to put harder limits on travel from the mainland to Hong Kong.