June 5 (Reuters) - The Russian rouble slightly extended a recovery from a more than five-week low against the dollar on Monday, supported by higher oil prices and companies' dividend plans as the country said it had repelled an offensive by Ukrainian forces.

By 1311 GMT, the rouble was 0.5% stronger against the dollar at 81.13, having hit 81.92 in early trade, its lowest since April 27. It had gained 0.8% to trade at 86.74 versus the euro and firmed 0.9% against the yuan to 11.38.

Russia said on Monday its forces had thwarted a major Ukrainian offensive at five points along the front in the Ukrainian region of Donetsk and killed hundreds of troops, while Kyiv accused Moscow of spreading lies.

While geopolitical risk remained a drag on the rouble, the currency was buoyed by other factors.

FX sales by Russian firms including oil major Lukoil , which is accumulating cash for dividend payments, should buttress the rouble.

"For the week we will likely see the dollar-rouble pair go below the 80 mark," said Promsvyazbank analyst Egor Zhilnikov. "The main support for the rouble could come from Lukoil's market activity on the backdrop of the company's dividend payments."

The rouble should also gain some support after the finance ministry said it would almost double its foreign currency sales in the coming month.

The market is also looking ahead to Friday, when the central bank is widely expected to keep rates on hold at 7.5%.

Brent crude oil, a global benchmark for Russia's main export, was up 2.1% at $77.75 a barrel, rising after Saudi Arabia pledged a deep cut to its output in July on top of a broader OPEC+ deal to limit supply into 2024.

Russian stock indexes also moved higher.

The dollar-denominated RTS index was up 0.2% at 1,053.5 points. The rouble-based MOEX Russian index was 0.2% higher at 2,723.5 points.

London-listed shares in gold and silver producer Polymetal were 2.6% lower after the company said it was considering divesting its Russian operations after they were targeted by U.S. sanctions. (Reporting by Alexander Marrow; Editing by Sriraj Kalluvila)