Hong Kong's acting chief executive on Tuesday called on pro-democracy protesters to clear sites they have occupied for more than six weeks and warned holdouts they could face arrest, a move that could swell protest numbers.

Hundreds of student-led demonstrators are camped out in two key districts of the Chinese-controlled city where they have pitched tents and set up supply stations on roads bisecting some of the world's most expensive real estate.

Hong Kong media reported that authorities could start removing protesters as early as Wednesday.