LONDON, Feb 1 (Reuters) - Retail group Bestway, the owner of Costcutter, has raised its stake in British supermarket group Sainsbury's (SBRY.L) to 4.47%, according to a regulatory filing published on Wednesday.

Last week, Bestway declared a 3.45% stake , describing the move as an investment and not a step towards making a takeover offer for Sainsbury's, which is Britain's second largest grocer after Tesco (TSCO.L) .

However, Bestway did say it may look to make further market purchases of Sainsbury's shares, subject to availability and price.

Shares in Sainsbury's were up 0.8% in morning trading, extending gains over the last month to 21.7%.

A spokesperson for Sainsbury's declined to comment beyond Friday's statement that the group would engage with Bestway in line with its normal interactions with shareholders.

A spokesperson for Bestway didn't immediately respond to a Reuters request for comment.

Bestway, which is owned by the Pervez, Choudrey and Sheikh families, is Sainsbury's sixth largest investor.

The Qatar Investment Authority (QIA) is the largest with 14.3%, while the second largest is Vesa Equity Investment, the vehicle of Czech billionaire Daniel Kretinsky, which has 10%.

Both have declined to comment on Bestway's investment.

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