LONDON, Aug 1 (Reuters) - British and Dutch wholesale gas prices inched up on Friday, supported by heavy maintenance at UK natural gas production facilities and continued uncertainty related to Russian supplies to Europe.

The British day-ahead contract was up by 21 pence at 285 pence per therm at 0946 GMT, while the contract for immediate delivery was 14 pence higher at 290 p/therm.

The front-month Dutch gas contract was up 7.00 euros at 198.50 euros per megawatt hour (MWh), while the contract for next-day delivery rose by 7.05 euros to 198.80 euros/MWh.

Natural gas production on the UK Continental Shelf (UKCS) is expected to drop from Monday by 23 million cubic metres (mcm) per day to 79 mcm, according to Refinitiv, due to multiple planned outages.

As a result, the UK system was more than 4 mcm undersupplied on Monday, according to the National Grid website.

Russian gas flows to Europe via Nord Stream 1 slightly increased, but uncertainty around the supplies kept the market on edge.

Russian gas producer Gazprom has reduced the capacity of Nord Stream 1, the major delivery route to Europe for Russian gas, to a fifth of its total capacity, citing maintenance issues.

However, the gas prices gains were capped due to arrivals of multiple liquefied natural gas (LNG) cargoes to UK terminals, and also an expectation of strong wind in coming days that could reduce British demand for gas for electricity production, Refinitiv analysts said.

UK peak wind power generation is forecast at around 11 gigawatts (GW) on Monday, rising to 15 GW on Tuesday, out of a total metered capacity of 19.9 GW, Elexon data showed.

"News from Australia, that the pressure to lower the LNG exports is building in order to supply the local market, is also keeping gas prices from easing further," said Hans van Cleef, senior energy economist at ABN AMRO.

In the European carbon market, the benchmark contract rose by 0.86 euros to 79.41 euros a tonne.

(Reporting by Bozorgmehr Sharafedin; Editing by Jan Harvey)