UK GAS-Prices continue to slide on rising supplies, weaker oil

* UK gas market undersupplied by 8 mcm/day

* Bacton Seal terminal restarts after an outage

May 19 (Reuters) - British wholesale gas prices continued to fall on Thursday on an expected increase in domestic supply, strong flows from liquefied natural gas (LNG) terminals and lower oil prices.

Gas for immediate delivery fell 0.25 pence to 30.00 pence per therm by 0845 GMT, while day-ahead contract lost 0.65 pence to 29.70 pence/therm.

With (Other OTC: WWTH - news) demand expected to be 224 million cubic metres (mcm) per day, and supply at 216 mcm/day, Britain's gas system was 8 mcm undersupplied, National Grid (LSE: NG.L - news) data showed.

Traders said prompt prices were weighed down by healthy supply from liquefied natural gas (LNG) terminals, with four tankers expected to arrive until May 25.

Gas market analysts at Thomson Reuters (Dusseldorf: TOC.DU - news) said they expected deliveries from LNG terminals to rise to 53 mcm/day from next week, up from around 50 mcm/day on Thursday.

Domestic supplies were also expected to rise after Total (LSE: 524773.L - news) 's Bacton Seal gas terminal started to ramp up flows on Thursday following a two-day outage.

Meanwhile, longer term contracts were pulled down by weaker oil market.

Further along the curve, contract for gas delivery in June , was trading at 29.00 pence/therm, 0.55 pence down, while gas for next winter also eased by 0.55 pence to 35.50 pence/therm.

Oil prices fell on Thursday, pulled down by unexpected rise in U.S (Other OTC: UBGXF - news) . crude inventories, a stronger dollar and surging output from Iran to Europe and Asia.

In the Netherlands, the day-ahead gas price at the TTF hub fell 0.22 euro/MWh at 12.93 euro/MWh.

In the European carbon market, front-year allowances eased 0.16 euro or 2.6 percent to 5.90 euro a tonne. (Reporting by Nerijus Adomaitis in Oslo; Editing by Greg Mahlich)