Russian Federation will "do everything to support the legitimate government of president Maduro", he said at a press conference.
Chinese Foreign Ministry spokesman Geng Shuang said historical experience showed foreign interference "only makes situations more complicated".
The trips have apparently paid off, as support for Guaido quickly poured in from right-wing governments in Latin America, in what the Financial Times called an "apparently co-ordinated move". Russia, Opec's biggest non-member ally, and China have both publicly denounced the U.S. sanctions on Venezuela.
Maduro accused an "oligarchy" in neighboring Colombia of being behind an attempt by military deserters to drive a wedge between himself and his loyal forces, which are key to the leader's hold on power faced with mounting worldwide support for self-proclaimed acting president Juan Guaido.
PDVSA began calling customers ahead of the sanctions, urging them to swap foreign fuel and other products for its Venezuelan crude cargoes, the sources said.
Venezuela's self-appointed president Juan Guaido has tried to wrest control of the country's state oil company, shortly before the United States imposed sanctions on the firm.
The Kremlin said this week it expected Venezuela to pay its debts.
The court also said prosecutors could investigate Guaido, in apparent retaliation for sweeping US sanctions on oil firm PDVSA, announced on Monday.
The US crude oil price has been rising since late December and could advance further as Washington imposes sanctions on Venezuela's state oil company.
The court move came after USA national security adviser John Bolton warned that the Maduro government would face "serious consequences" if Mr Guaido is harmed.
Venezuela is very reliant on the US for its oil revenue.
In a nation awash with rumors amid a government crisis in which two men have claimed Venezuela's presidency, even the unexpected arrival of a Russian passenger jet can set off a social media frenzy.
Pompeo determined that Guaido has authority over the nation's accounts at the Federal Reserve Bank of NY and other USA -insured banks, State Department deputy spokesman Robert Palladino said in a statement. The US, which buys more than 40 per cent of Venezuela's crude, is the South American country's single biggest oil customer.
The US slapped oil sanctions on Maduro's regime earlier this week in an attempt to starve the government of its funding.
US Treasury Secretary Steven Mnuchin said the sanctions against PDVSA would prevent Maduro from diverting resources from the country until power could be transferred to an interim or democratically-elected government.
"Hands off Venezuela", Maduro said forcefully in a direct message to Trump.
China will continue advancing cooperation with Venezuela in various fields based on the principles of equality, mutual benefits and common development, he added.