The announcement represented a continuing drive by Kiev's new pro-Western leaders to tie their economic future to Europe and sever a decades-old dependence on the Kremlin that many Ukrainians feel has shackled their political rights.
But it also threatens to infuriate Moscow and complicate Statoil's effort to become one of the first global majors to access the potentially enormous wealth of untapped Arctic energy fields.
It signed a broad Arctic agreement with Russia's oil powerhouse Rosneft now the target of EU and US sanctions that are meant to punish the Kremlin for its actions in Ukraine in 2012.
"The agreement marks a significant breakthrough for Naftogaz," chief executive Andriy Kobolev said in a statement.
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"We are committed to integrating Ukraine fully into the EU energy market and working with the European Commission and other key actors to do so."
Russia nearly doubled Ukraine's gas price a few weeks after the February ouster in Kiev of a Kremlin-backed president who had earlier rejected a historic EU trade and political association pact.
A new round of EU-mediated talks between Moscow and Kiev failed to resolve the dispute last week and another meeting is still under discussion.
Ukraine has tried to make up some of this year's shortage by boosting purchases from its western neighbours.
But Russia warned last week that it may be forced to interrupt European supplies because of a handful of nations' decision to re-export gas to Ukraine in breach of their Gazprom contracts.
But Hungary immediately halted its limited shipments to Ukraine -- a decision Gazprom rewarded by boosting the former Soviet satellite's gas supplies.