Poland Under-21 international Bielik, 21, has agreed a five-year contract with the Championship club.

He spent last season on loan with Charlton, making 34 appearances as the Addicks were promoted from League One.

Centre-back Clarke, 22, joined the Seagulls in June, having featured 175 times over four seasons at Portsmouth.

Bielik, who can also play in defence, joined Premier League club Arsenal from Polish outfit Legia Warsaw in January 2015 but he only made two senior outings for the Gunners, which both came in the League Cup.

He spent time on loan at Birmingham City and Walsall before agreeing a season-long move to Charlton last August.

"He is a young player and it is a permanent deal, which I think is a very good investment for the club," Derby boss Phillip Cocu said.

"I am very happy he has joined the team.

"He will get better and develop, but for his age he is a very good player."