Feb 15 (Reuters) - JB Hi-Fi Ltd said strong sales have continued into January after posting an 86% rise in first-half profit on Monday, driven by a surge in online sales as consumers spent heavily on electronics amid COVID-19 lockdowns.

The electronics retailer did not provide sales or earnings forecasts for fiscal 2021, but reported January comparable sales growth of 18.6% for JB Hi-Fi Australia and 14.1% for The Good Guys, its biggest earners.

The Melbourne-based firm declared an interim dividend of A$1.80 per share, compared with A$0.99 a year ago.

Its shares rose over 2% to A$51.95, set for their biggest percentage gain in a week after four straight sessions of losses.

"In what is an uncertain environment we continue to adapt and respond and, with a number of opportunities ahead of us, we remain excited by the outlook for the business," said Richard Murray, chief executive of JB Hi-Fi.

The retailer said net profit after tax grew to A$317.7 million ($246.6 million) for the half-year ending Dec. 31, in line with previously issued guidance, while online sales more than doubled to A$678.8 million.

Brokerage Jefferies sounded a note of caution, saying that while sales growth remained elevated into January, sales for both JB Hi-Fi Australia and the Good Guys slowed relative to the fourth-quarter run rate.

"We believe stock availability may be starting to weigh on sales rather than demand."

Electronics and household goods retailers have benefited as the coronavirus pandemic forced people to work from home, while massive stimulus measures and strong household savings have kept retail sales afloat, with few other avenues open for spending.

($1 = 1.2883 Australian dollars) (Reporting by Arpit Nayak in Bengaluru; Editing by Richard Pullin)