At least seven people have been killed during unrest in Venezuela following mass protests against the South American country's president Nicolas Maduro.
Hundreds of thousands of demonstrators took to the streets across the country in a bid to topple the socialist leader, who is clinging onto power amid political and economic crisis.
Juan Guaido, the new leader of the opposition-controlled National Assembly, declared himself the country's interim president as he addressed cheering crowds in the capital Caracas on Wednesday.
The demonstrations had been planned by a newly invigorated opposition to coincide with the anniversary of the end of Venezuela's last military dictatorship in 1958.
Tensions have been escalating since Mr Maduro took office for a second six-year term on January 10 following a widely boycotted election, described by several foreign governments as a sham.
Russia accused the United States of trying to usurp power in Venezuela and warned against US military intervention there, putting it at odds with Washington and the EU which backed protests against one of Moscow's closest allies.
Mr Guaido declared himself interim leader on Wednesday, winning the support of Washington and parts of Latin America and prompting Mr Maduro, who has led the oil-rich nation since 2013, to sever diplomatic ties with the United States.
The prospect of Mr Maduro being ousted is a geopolitical and economic headache for Moscow which, alongside China, has become a creditor of last resort for Caracas, lending it billions of dollars as its economy implodes. Moscow has also provided support for its military and oil industry.
Last night Russia accused Washington of stoking street protests and of trying to undermine Mr Maduro, whom it called the country's legitimate president.
"We consider the attempt to usurp sovereign authority in Venezuela to contradict and violate the basis and principles of international law," Kremlin spokesman Dmitry Peskov said.
He said Russia had not received a Venezuelan request for military help and declined to say how it would respond if it did.
Mr Maduro, who met Vladimir Putin in Moscow in December, was the legitimate president, said Mr Peskov.
The Russian Foreign Ministry weighed in too, complaining that Washington was seeking to determine the fate of other nations by using a well-tried strategy of trying to depose an undesirable government.
It told Washington not to intervene militarily, warning outside interference was the path to bloodshed.
"We warn against such adventurism which is fraught with catastrophic consequences," it said.
Turkish President Tayyip Erdogan offered support for Mr Maduro too.
"My brother Maduro! Stand tall, we stand by you!" presidential spokesman Ibrahim Kalin, writing on Twitter, quoted Mr Erdogan as saying.
China, a major lender to Caracas, also voiced its support for Mr Maduro, saying it opposed outside interference in Venezuela and supported efforts to protect its independence and stability.
The European Union, which has imposed sanctions on Venezuela and boycotted Mr Maduro's swearing-in for a second term earlier this month, took a different tack.
Although it stopped short of following Washington and recognising Mr Guaido as interim president, it called on the authorities in Venezuela to respect his "civil rights, freedom and safety" and appeared to support calls for a peaceful transition of power away from Mr Maduro.
"The people of Venezuela have massively called for democracy and the possibility to freely determine their own destiny. These voices cannot be ignored," the 28-nation bloc said in a statement.
French President Emmanuel Macron saluted the courage of Venezuelans marching for freedom and called Mr Maduro's 2018 election victory illegal. A spokesman for British Prime Minister Theresa May said the election has been neither free nor fair and expressed support for Mr Guaido as national assembly head.
Venezuela's military has shown no sign of leaving Mr Maduro's side. Defence Minister Vladimir Padrino reaffirmed his support in a tweet, saying Venezuela's armed forces disavowed any self-proclaimed president.
The Supreme Court, stacked with Maduro loyalists, has remained solidly behind the socialist leader, ruling earlier this week that all actions taken by the congress - led by Mr Guaido - are null and void.