UK GAS-Prompt prices fall due to rising supplies from Norway

* Nyhamna gas processing plant outage ends

* Gas system oversupplied by 17 mcm/day

* Limited impact from Brexit on gas markets in short-term

June 28 (Reuters) - British wholesale gas prices fell on Tuesday morning as higher imports from Norway and rising domestic supply left the gas system oversupplied.

Gas for immediate delivery fell by 0.35 pence to 33.70 pence per therm by 0830 GMT, while the day-ahead contract lost 0.75 pence to 33.90 pence/therm.

"The jump in Langeled flows has resulted in an oversupplied market," said Oliver Sanderson, gas market analyst at Thomson Reuters.

The gas network was oversupplied by 17 million cubic metres/day (mcm), with daily demand estimated at 153 mcm/day, National Grid (LSE: NG.L - news) data showed.

Imports from Norway via Britain's main subsea gas import route, the Langeled pipeline, rose by 7 mcm after an outage at Norway's Nyhamna gas processing plant ended on Tuesday morning.

In addition, deliveries into St Fergus Mobil terminal rose slightly and an outage at Centrica (LSE: CNA.L - news) 's North Morecambe gas sub-terminal was expected to end on Tuesday afternoon, earlier than previously planned.

St Fergus TOM terminal is also expected to ramp up gas flows after ongoing maintenance is expected to end on Wednesday.

Last week's shutdown of Britain's Rough gas storage site - the country's largest - for 42 days has led to a drop in overall demand because it is not possible to replenish stored reserves.

Further along the curve, the contract for gas delivery next-month eased by 0.4 pence to 33.80 pence/therm, while the benchmark winter 2016 contract was unchanged at 42.65 pence/therm.

In the Netherlands, the day-ahead gas price at the TTF hub rose 0.18 euro to 14.23 euros per MWh.

So far, Britain's vote to leave the European Union hasn't had a major impact on European gas markets, with prices reacting more to the Rough outage and a reduction in gas production from the Dutch Groningen field, UK-based consultancy Energy Apsects said.

"In the short-term, Brexit will have limited impacts on the European gas market, feeding through from the loss in business confidence and the huge uncertainty now facing the UK," the analysts said.

"In the medium term, flows are unlikely to change significantly although there is a risk that energy trade could face border charges. With cooler weather forecast to dominate the next two weeks, prices are likely to moderate to below the 14.58 euro per megawatt hour price trigger level," they added.

In the European carbon market, front-year allowances firmed by 0.10 euro to 4.87 euros a tonne. (Reporting by Nerijus Adomaitis; editing by Nina Chestney)