BERLIN/LONDON (Reuters) – Physical gas flows through the Nord Stream 1 pipeline from Russia to Germany plunged on Monday morning as maintenance of the pipeline got underway, operator data showed.

Physical flows dropped to 439,720 kilowatt-hours per hour (kWh/h) on Monday, from 9 am to 10 am, compared with physical flows over 29 million kwh/h earlier in the morning and over most of the previous day.

Nord Stream 1 started annual maintenance on Monday, with flows expected to stop until maintenance ends on July 21, but governments, markets and companies are worried the shutdown might be extended due to war in Ukraine.

Nominations for Russian gas flows into Slovakia from Ukraine via the Velke Kapusany border point stood at 37.8 million cubic metres (mcm) per day, up from 36.9 mcm the previous day, data from the Ukrainian transmission system operator showed.

Russian gas producer Gazprom said its supply of gas to Europe through Ukraine via the Sudzha entry point was seen at 39.4 mcm on Monday compared with 41.9 mcm a day earlier.

Eastbound gas flows via the Yamal-Europe pipeline to Poland from Germany rose on Monday morning, data from pipeline operator Gascade showed.

Exit flows at the Mallnow metering point on the German border were at 4,803,874 kWh/h, up from levels around 4,100,000 kWh/h for much of the previous day.

(Writing by Rachel More and Susanna Twidale, Editing by Miranda Murray Editing by Louise Heavens and Louise Heavens)