US Vice President Joe Biden told Russia today it faced paying an ever-higher price over Ukraine as tensions ratcheted up on the first anniversary of mass protests which unleashed a year of turmoil.
Biden described as "unacceptable" the Kremlin's role in the crisis in eastern Ukraine, where Moscow denies giving military assistance to pro-Russian separatists in a seven-month conflict which has killed 4,300 people.
Hinting at possible new sanctions, he warned Russia had failed to fulfil its commitments under a September peace plan, adding: "So long as that continues, Russia will face rising costs, greater isolation."
Meanwhile, crowds gathered in Kiev's Independence Square, known as Maidan, to remember the more than 100 people who died in demonstrations that started on November 21 last year.
Ukrainian President Petro Poroshenko was heckled by relatives of the dead shouting "Shame!" over the authorities' failure to convict anyone over the deaths as he laid a candle at the shrines.
Mourners left flowers and wept or crossed themselves, while others said fresh protests were needed to bring real change to Ukraine, where corruption is rife.
"Of course, we are disappointed. Nothing changed," said Petro Runkiv, a 58-year-old civil engineer who took part in the protests.
"We need reforms and we are here to let our government know that we are ready for one more Maidan."
On a frantic day of diplomacy, Ukraine's leaders also announced the formation of a five-party parliamentary coalition comprising the groupings of President Petro Poroshenko, Prime Minister Arseniy Yatsenyuk and former premier Yulia Tymoshenko.
The coalition will, for the first time, be strong enough to pass amendments to the constitution and comes after elections in October.
