Akhmed Zakayev left Poland on Sunday because his Polish visa was expiring, Adam Borowski told The Associated Press.

Zakayev was taken into custody in Poland on Friday but released that evening after a Warsaw court rejected the Russian-issued warrant for his arrest.

Russia wants the 51-year-old Zakayev, who lives in exile in Britain, on charges related to Chechnya's separatist war of the 1990s, but has so far been unsuccessful in getting any country to extradite him. Courts in Britain and Denmark have previously rejected extradition requests.

Zakayev maintains the accusations against him are trumped up by Moscow.

However, Polish Justice Minister Krzysztof Kwiatkowski said Monday that the case was not yet formally closed, because Russia could still demand Zakayev's extradition.

Also, Polish prosecutors were weighing whether to appeal the court's decision to release him.

Zakayev will seek to extend his visa so that he can return to Poland in case of any future court proceedings, Borowski told the AP.

Zakayev on Saturday attended a conference on Chechnya's future in Pultusk, in central Poland.