Sept 5 - Activist investor Elliott Investment Management's stake in Swedish Match crossed 5% on Friday, making it the biggest shareholder in the tobacco and nicotine products maker that is currently subject to a takeover offer by Philip Morris.

Bloomberg News reported in July, citing sources familiar with the matter, that Elliott was building a stake in the Stockholm-based firm in an attempt to oppose the nearly $16 billion buyout deal under its current terms.

In a filing to Sweden's financial watchdog Finansinspektionen on Friday, Elliott said it had increased its stake in Swedish Match to 5.25%. The size of its previous holding was not disclosed.

On its website, Swedish Match lists Wellington Management as its biggest shareholder with a 5.1% stake, followed by Capital Group and BlackRock with 4.8% and 4.6% respectively.

Swedish Match and Elliott declined to comment on the change in Elliott's holding. Philip Morris did not immediately respond to Reuters' requests for comment.

The Marlboro maker last month extended the acceptance period of its May bid until Oct. 21 from Sept. 30, and said it had so far received acceptances for around 0.24% of the shares.

Under Swedish law, 90% of shareholders need to agree to the deal for it to proceed.

Swedish Match stakeholders who have previously opposed the takeover include hedge fund Bronte Capital and investment firm abrdn.

Bronte has said it holds 1% in the company, while abrdn owns 0.3%, according to Refinitiv data. (Reporting by Marie Mannes in Gdansk; Editing by Milla Nissi and Jan Harvey)