Naftogaz Ukrainy had paid Russia's Gazprom $1.28 billion of its debt for gas supplied in 2013 as of February 14, says the prospectus for a Ukrainian sovereign eurobond placement, seen by Interfax-Ukraine.

Naftogaz had also paid $191 million for gas supplied in January.

Gazprom has said Naftogaz owed it $2.63 billion for gas supplied in 2013 and was due to pay another $660 million for gas supplied in January by February 7.