Russia's oil export flows have been disrupted since April when high levels of organic chloride were found in crude pumped via the Druzhba pipeline to the Baltic port of Ust-Luga and elsewhere in Europe via Poland.

Total said that "due to the prolonged exceptional situation on the Russian crude contaminated with high levels of organic chloride, Total Raffinerie Mitteldeutschland GmbH (Leuna) had to take some units of the refinery out of operation last week in order to make appropriate technical checks."

Operations at the refinery started to resume at the beginning of the week, using uncontaminated crude that was stored in Germany, it added.

But continuing problems with the Druzhba pipeline meant the refinery's capacity will remain limited for now.

Leuna and Schwedt, another big refinery in north eastern Germany and thus also receiving Russian oil via Druzhba, are receiving some alternative shipments of uncontaminated oil via the ports of Gdansk and Rostock on the Baltic Sea.

A spokesman for the German mineral oil industry group MWV in Berlin said the Druzhba pipeline was still shut for the time being, but supply security was not in danger.

"Domestic supply with mineral oil products is still ensured," he said.

MWV represents 14 member companies, 17 refinery sites with 103 million tonnes of processing capacity, and 10 oil pipelines.

(Reporting by Geert De Clercq and Vera Eckert, editing by Richard Lough and David Evans)