UK GAS-Prices rise as Russian supply worries prompt storage buying

* Ukraine crisis escalates, supply worries resurface

* Flows along Langeled pipeline surge to 66 mcm/day

* Substantial storage injections expected

LONDON, April 14 (Reuters) - British natural gas prices rose on Monday morning as traders took advantage of a surge in Norwegian flows to prepare for a potential Russian supply cut by buying gas to inject into storage.

Gas for delivery on Tuesday was up 0.50 pence to 52.50 pence per therm by 0900 GMT, while gas for delivery next winter climbed 1.54 pence to 65.75 pence per therm.

Gas for within-day delivery fell 0.65 pence to 52.00 pence per therm due to weak demand and an oversupplied system.

Tensions between Ukraine and gas exporter Russia intensified over the weekend as Ukraine's acting president warned of a major military crackdown on pro-Russian separatists in eastern Ukraine.

Moscow has threatened to cut off gas supplies to Ukraine, a major transit route for Russian gas to Europe. It has also sharply raised the price Ukraine must pay for gas and says Kiev owes it more than $2 billion in unpaid gas bills.

"If the market is starting to seriously consider a drop in Russian flows later in the summer, it would be ideal to take advantage of Norwegian spare production capacity and inject high volumes of gas into storage now," an analyst said.

On Monday, flows along the Langeled pipeline from Norway's gas fields in the North Sea rose dramatically to 66 million cubic metres (mcm) per day, roughly three times Friday's figure.

Norway also postponed planned maintenance on its Continental (Frankfurt: CON.F - news) Shelf until Wednesday.

That left Britain's gas system roughly 34 mcm oversupplied, with flows seen at around 246 mcm per day and demand at around 212 mcm, data from the National Grid (LSE: NG.L - news) showed.

Demand for gas has been well below the seasonal norm in recent weeks as mild weather lowers the need for heating, and meteorologists say temperatures will remain mild for most of this week.

In Britain's power markets, prices for baseload (24 hours) delivery on Tuesday rose 1.32 pounds ($2.21) to 43.60 pounds per megawatt-hour as wind production was expected to drop sharply. ($1 = 0.5980 British Pounds)

GAS UK natural gas prices National Grid instant flows National Grid gas demand North Sea gas and power maintenance

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(Reporting by Alexander Winning; editing by Jason Neely)