Aug 13 (Reuters) - Bitcoin miner Riot Platforms ( RIOT )

said on Tuesday it had increased its stake in rival Bitfarms ( BITF )

to 18.9%.

Riot acquired 1 million common shares of Bitfarms ( BITF ) on

Tuesday, representing about 0.22% of issued and outstanding

Bitfarms ( BITF ) common stock.

The acquisition takes the total count of Bitfarms ( BITF ) shares

owned by Riot to about 85.3 million.

Bitfarms ( BITF )

said

earlier in the day its co-founder and chair Nicolas Bonta,

one of the three board members top shareholder Riot sought to

replace, would leave the company immediately.

The two companies have been locked in a dispute since

April, when Riot made an unsolicited $950-million offer to

acquire Canada-based Bitfarms ( BITF ).

Bitfarms ( BITF ) said the bid undervalued it significantly and

adopted a

"poison pill"

to fend off any attempt at a hostile takeover. A poison

pill refers to shareholder rights plans used by corporate boards

to thwart hostile takeover bids.

Riot withdrew its offer at the time, but is now seeking

three seats on the Bitfarms ( BITF ) board and has said it is "ready to

engage" with the reconstituted board on a potential transaction.