The 1994 document assured Ukraine of Western and Russian protection from foreign invasion in return for scrapping its Soviet-era nuclear arsenal and accession to the Non-Proliferation of Nuclear Weapons Treaty.

"We have irrefutable evidence from both satellite imagery and video footage captured by our intelligence service showing that the Ukrainian border was crossed by Russia's latest military equipment and armed forces units," Poroshenko said.

Months of laborious European-mediated negotiations have failed to bring a complete halt to a war that has now claimed more that 9,000 lives and left some of Ukraine's most important coal mines and steel mills in ruins.

"In 2016, we must also ensure the renewal of Ukraine's sovereignty over the occupied territories of Luhansk and Donetsk," Poroshenko said.

A new round of talks between top Moscow and Kiev envoys produced a new ceasefire agreement on Wednesday that appeared to be largely holding on Thursday afternoon. (afp/ez)