* Gas system undersupplied by 10 mcm/day
* Crude oil prices clime over $50 a barrel
* Kollsnes, Troll field to be shut on May 28-June 9
May 26 (Reuters) - British gas prices rose on Thursday as lower supplies from Norway left the system undersupplied and oil prices climbed to a near seven-month high.
Gas for immediate delivery rose 0.65 pence or 2.2 percent to 30.20 pence per therm by 0900 GMT, while day-ahead contract gained 0.35 pence or 1.18 percent to 29.95 pence/therm.
Gas imports from Norway fell by 9 mcm to 72 mcm/day, mainly due to lower deliveries via the Langeled pipeline, Britain's main subsea gas import route.
Deliveries could fall further on Friday as Norway's Kollsnes gas processing plant is set to begin planned maintenance.
Both Kollsnes and Norway's biggest gas field, Troll, will be completely shut for maintenance from May 28 until June 9.
Gas exports from Britain to Belgium rose to near maximum levels of 44 mcm/day, offsetting a decrease in domestic demand due to warmer weather, traders said.
Brent oil futures topping $50 a barrel for the first time since October supported gas prices further along the curve. Carbon prices also rose.
Contract for gas delivery next winter was trading at 35.80 pence/therm, up 0.25 pence from the previous session.
In the European carbon market, front-year allowances rose by 0.19 euro or 3.2 percent to 6.06 euro a tonne.
Dutch day-ahead prices at the TTF hub gained 0.12 euro/MWh to 13.30 euro/MWh.
(Reporting by Nerijus Adomaitis in Oslo; editing by Jason Neely)