The Russian rouble dropped to its weakest against the euro since late May on Tuesday, hurt by relatively low oil prices and the prospect of lower export revenue due to the price cap on Russian oil which came into force this month.

By 0732 GMT, the rouble had lost 0.9% to trade at 66.94 versus the euro, its weakest since May 30. It eased 0.8% against the dollar to 63.31 and had shed 0.9% against the yuan to 9.07.

"The rouble has weakened against all major competitors," said Otkritie Research in a note. "The sanctions theme continues to put pressure on the Russian currency."

Russia's economy and government finances are set to struggle under the weight of the European Union's embargo of Russian oil exports and a $60-a-barrel price cap imposed by the G7, the European Union and Australia.

Brent crude oil, a global benchmark for Russia's main export, was up 1.8% at $79.4 a barrel, having last week hit its lowest level this year.

Investors are also keeping an eye on the Bank of Russia, which is expected to hold its key interest rate at 7.5% on Friday, as inflation continues to slow and in order to assess the possible economic impact of the oil price cap and embargo, according to a Reuters poll.

Markets also are awaiting a flurry of other interest rate decisions this week, including from the U.S. Federal Reserve and the European Central Bank.

Russian stock indexes were mixed.

The dollar-denominated RTS index was down 0.7% to 1,081.3 points. The rouble-based MOEX Russian index was unchanged at 2,173.1 points.

For Russian equities guide see

For Russian treasury bonds see (Reporting by Alexander Marrow; Editing by Kirsten Donovan)