"We are pleased to have signed a dangerous player who will surely be a help to us," a statement on Dortmund's official site read.

Rangelov, whose new contract details were not revealed, scored 15 goals over the past two season for the relegated Cottbus.

The 26-year-old joins Mohamed Zidan, Nelson Valdez and Alexander Frei in Jurgen Klopp's strikers department.

"I want to score many goals. And I want to help the club to play in Europe again soon," said the Bulgaria international.