LONDON, June 13 (Reuters) -
* British wholesale gas prices rose on Thursday morning, with prices lifted by an under-supplied market and strong gains in oil following a suspected attack on two tankers in the Gulf of Oman near Iran.
* Within-day gas price up 1.47 pence at 30.60 pence per therm by 0855 GMT.
* Day-ahead gas price up 0.55 p at 29.75 p therm.
* "Under-supply is lifting the prompt and the oil news is having more impact supporting the curve,” a gas trader said.
* Oil prices surged as much as 4% on Thursday after a suspected attack on two tankers in the Gulf of Oman near Iran and the Strait of Hormuz, through which a fifth of global oil consumption passes.
* Forward gas contracts are sensitive to swings in oil markets due to a long-standing practice which fixes some long-term gas contracts to crude prices.
* UK gas system under-supplied by 14.6 million cubic meters (mcm) with demand forecast at 220 mcm and flows at 205.4 mcm/day, National Grid data showed.
* Traders said a drop in wind power output expected on Friday led to anticipation of higher demand for gas.
* Peak wind power generation is forecast at 10 gigawatts (GW) on Thursday, falling to 5.5 GW on Friday, National Grid data showed.
* Further out on the curve, prices also rose.
* July contract up 0.56 p at 28.48 p/therm.
* Winter 2019 contract up 0.50 at 52.70 p/therm.
* Day-ahead gas price at the Dutch TTF hub up 0.05 euro at 11.25 euros per megawatt hour.
* Benchmark Dec-19 EU carbon contract up 0.11 euro at 24.93 euros per tonne. (Reporting by Susanna Twidale; Editing by Mark Potter)