The Kremlin "cannot officially confirm" reports that Russia and Ukraine have reached a natural gas agreement, Russian President Vladimir Putin's spokesman said.

"At the moment we cannot officially confirm that there is an agreement. In case such an agreement is recorded by the two sides, we will naturally announce this immediately," Dmitry Peskov said in answering a question from Interfax.

In a comment on an allegation that the Russian and Ukrainian governments have clinched a gas deal not linked to Ukraine's proposed entry into the Customs Union, Peskov said there are expert- and high-level contacts between the two countries, and that "the gas issue is on the agenda of bilateral relations."