Kowloon Motor Bus (KMB) on Saturday said it's not ruling out applying for a fare hike this year, after operating costs rose.

The higher costs also included its investment in electric buses, with a new batch of electric double-decker buses beginning a phased roll-out on Saturday.

But the franchised bus operator called for more government subsidies, saying it's incurred higher costs from its spending on electric buses.

The company said earlier that it wouldn't rule out seeking a fare hike, but Kenny Kan, head of the company's corporate communications and public affairs department, stressed that the increased costs from electric buses were just one factor in this. .

"Costs - whether fuel or labour - have increased. As a bus operator, our fiscal robustness and sustainability is very important," he said.

"If we think there's a need, we'll definitely apply for a fare hike... But in terms of how much the hike would be, we would consider the issue of affordability."

The KMB imported 52 electric double-decker buses, and 44 are currently in service.