MOSCOW, Jan 12 (Reuters) - The Yamal-Europe pipeline, which usually sends Russian gas west into Europe, instead flowed east from Germany to Poland for the 23rd day on Wednesday, data from German network operator Gascade showed.

Since Dec. 21, the link between Poland and Germany had been operating in reverse mode, carrying gas from west to east and putting upward pressure on European gas prices.

The pipeline accounts for about one sixth of Russia's normal annual gas exports to Europe and Turkey.

Eastbound volumes stood at 8.7 million kilowatt hours an hour (kWh/h), up from 7 million kWh/h seen earlier this week, and are expected to remain in reverse until early hours on Thursday, data from the Mallnow metering point on the German-Polish border showed.

It is not clear when the pipeline will change the flows back towards Germany, though a source close to Gazprom said the company is expected to switch flows back at some point this month, as Gazprom has paid for westbound volumes.

Capacity nominations for Russian gas flows from Ukraine to Slovakia via the Velke Kapusany border point, another major route for Russian gas to Europe, stood at 287,362 megawatt hours (MWh) per day.

That level was steady compared to nominations seen over the past week but remained below levels of more than 900,000 MWh recorded in early December, data from Slovak pipeline operator Eustream showed.

(Reporting by Katya Golubkova; Editing by Rashmi Aich)