Ukraine's acting interior minister has confirmed two people have been killed and several injured in a shootout in the eastern Ukrainian city of Kharkiv.
Arsen Avakhov wrote on his official Facebook page early on Saturday that around 30 people "from both sides" were arrested late on Friday evening. Gunshots were heard in the area.
Russian state news agency Itar Tass reported that the clash occurred outside a building of the far-right Ukrainian nationalist group, Right Sector, although Avakhov made no mention of the group and said the incident was under investigation.
Both sides blamed each other for the violence overnight.
The clashes come after a six-hour meeting between the US Secretary of State and Russian Foreign Minister failed to reach an agreement on how best to end the crisis in Ukraine on Friday.
The meeting, set in the official residence of the US ambassador in central London, comes two days before a referendum on 16 March where Crimeans will decide whether the region should be claimed by Moscow, or remain in Ukraine, following Russia’s military seizure of Crimea earlier this month.
After the negotiations, John Kerry maintained the Western view that the referendum is illegitimate because of the presence of thousands of Russian troops on the Crimean streets combined with the lack of a significant campaign period.
But Sergei Lavrov said Moscow will continue to “respect” the result of Sunday’s referendum.
Mr Lavrov also rejected calls from Western powers to create an international contact group to resolve the crisis in Ukraine, citing “the crisis was not caused by Russia” and that “the relationship [between Russian and Ukraine] had never been ceased”. The UN Security Council will vote today on a US-drafted resolution that would define the Crimea referendum as illegal.
The resolution being put to a vote would reaffirm the council's commitment to Ukraine's territorial integrity and declare that tomorrow's referendum on whether Crimea should become part of Russia "can have no validity, and cannot form the basis for any alteration of the status of Crimea".
Acting president Oleksander Turchinov, who reviewed large Ukrainian military exercises on Friday, has said the massing of Russian troops showed they were "ready to invade ... at any moment".
But Mr Lavrov said on Friday that Moscow had no plans to invade southeastern Ukraine.
Additional reporting by agency
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