Reuters reports that Venezuela's debt repayment to Russia has slowed down to a trickle:

The head of Russian oil company Rosneft (ROSN.MM), Igor Sechin, flew to Caracas this week to meet Venezuelan President Nicolas Maduro and complain over delayed oil shipments designed to repay loans, two sources briefed on the conversation said on Saturday.

The visit, which was not publicly disclosed, is one of the clearest signs of strain between crisis-stricken Venezuela and its key financier Russia.

Over the last few years, Moscow has become Venezuela's lender of last resort, with the Russian government and Rosneft handing Venezuela at least $17 billion in loans and credit lines since 2006, according to Reuters calculations.

State oil company PDVSA is repaying almost all of those debts with oil, but a meltdown in its oil industry has left it struggling to fulfill obligations.