In November 2005, Altimo acquired 49% of the Cukurova shares for $3.3 billion and granted the Turkish company a $1.707 billion loan.
The deal enabled Altimo to gain a 13.22% indirect stake in Turkcell, Turkey's largest mobile phone operator. In November 2006, Cukurova paid $357 million as principal, and $217 million as interest.
However, Cukurova defaulted on its loan commitments afterwards, Altimo said.
"Altimo is concerned that, following a number of event defaults by Cukurova, the security of its loan is compromised. Cukurova has repeatedly failed to comply with the agreements signed in 2005. Altimo has to put in place measures to protect its position in relation to the outstanding loan," Altimo's statement said.
Altimo has also referred the matter to a court in the British Virgin Islands to seek confirmation of its position, the statement said.
Altimo plans to merge with a major European operator, Altimo's chief executive Alexei Reznikovich said.
"We plan to cooperate with a major European operator. A merger trend is evident on the market, and Europe's telecoms structure will be completely different in three to four years. We believe it is very important for us to participate in this process," Reznikovich said.