UK GAS-Prompt prices rise as imports from Norway fall

* UK gas market 7 mcm undersupplied

* Flows through Langeled drop to around 25 mcm

June 21 (Reuters) - British prompt gas prices rose on Tuesday morning, as imports from Norway fell, leaving the British gas system undersupplied.

Gas for within-day delivery fetched 35.30 pence per therm at 0806 GMT, up 0.40 pence from their last settlement.

Gas for day-ahead delivery rose 0.05 pence to 35.15 pence per therm.

British imports from Norway via Langeled, Britain's main gas import pipeline, stood at around 25 million cubic metres (mcm), down from more than 40 mcm the previous day, National Grid (LSE: NG.L - news) data showed.

With (Other OTC: WWTH - news) supply flows at 168.5 mcm and demand expected to be 175.5 mcm/day, Britain's gas system was 7 mcm undersupplied, the data showed.

Gas prices further along the curve fell, dragged lower by weaker oil prices, traders said.

The Winter '16 gas contract was down 0.15 pence at 41.60 pence per therm.

The Brent crude front-month contract was down by around 50 cents a barrel, trimming the 3 percent gain made on Monday as concerns eased about Britain leaving the European Union.

Analysts said energy markets are likely to be volatile ahead of Britain's EU referendum on Thursday.

"A vote to leave could well see panic in the financial markets - with sterling likely to be the heavy loser from a Brexit vote. This would certainly be bullish for NBP (UK gas) against TTF (Dutch gas)," analysts at Energy Aspects said in a research note.

Should Britain vote to remain in the EU, the pound would likely rise against the euro which would be bearish for British gas prices, the analysts said.

In the Netherlands' gas market, the day-ahead price at the TTF hub was up 0.1 euro at 15.10 euros per megawatt-hour.

In Europe's carbon market, the front-year EU allowance price was down by 0.05 euro at 5.81 euros per tonne. (Reporting by Susanna Twidale; editing by Jason Neely)