Russia's foreign minister Sergei Lavrov has warned that Moscow will "respond" if its interests in Ukraine are attacked.
Speaking on Russian-owned television channel RT, Mr Lavrov said Washington's "ready-made solutions" will not fix the crisis in Ukraine and insisted that the US "cannot run the show in each and every part of the globe".
He warned that Russia would "respond" if the interests of Russian citizens in the region are threatened by Ukraine's actions, drawing a parallel to the 2008 Georgian war.
"If our interests, our legitimate interests, the interests of Russians have been attacked directly, like they were in South Ossetia for example, I do not see any other way but to respond in accordance with international law," he added.
Although he did not elaborate on what such a response would be, he insisted that an attack on a Russian citizen is "an attack on the Russian Federation" and Moscow would respond accordingly. Meanwhile, Kiev fears that Russia could use that as pretext to send troops and seize Ukrainian territory.
Mr Lavrov's warning comes just hours after Ukraine's acting president Oleksandr Turchynov ordered security forces to resume anti-terrorism operations after the bodies of two people allegedly abducted by pro-Russia insurgents were found "brutally tortured" in eastern Ukraine.
The Russian foreign minister said it was "quite telling" that the government in Kiev, which Russia does not recognise, relaunched its anti-terror operations coinciding with US vice president Joe Biden's visit to Ukraine earlier this week.
On Tuesday, Mr Biden warned Russia it was time to "stop talking and start acting" to defuse tensions in the troubled region and called on President Vladimir Putin to pull back Russian troops deployed close to Ukraine’s border in Russia.
"We’ve heard a lot from Russian officials in the past few days. But now it’s time for Russia to stop talking and start acting," he told reporters. "We will not allow this to become an open- ended process. Time is short in which to make progress."
His remarks were echoed by secretary of state John Kerry, who warned Moscow more sanctions could follow in the absence of diplomatic progress.
The Kremlin says its military operations along the Ukrainian border are within the bounds of international law and has repeatedly denied it has deployed special forces in eastern Ukraine to fuel civil unrest despite Kiev's accusations.
Mr Lavrov added: "No one who participated in the inspections, including the Americans, Ukrainians and Europeans, have ever brought up any facts that would indicate Russia was engaged in some dangerous military activity."
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