The investment arm of Israeli gas firm Delek Group Ltd. has acquired a near 20% stake in North Sea-focused oil producer Ithaca Energy Inc. for $66 million, the companies said on Oct. 9.

The deal underlines investors still see value in North Sea related businesses, despite a slump in oil prices and high operating costs in one of the world's most mature oil and gas basins.

Ithaca, whose London-listed shares have sunk more 60% since the oil price started to decline in June 2014, said it would use Delek's investment to strengthen its balance sheet and reduce debt.

Ithaca's London-listed stock was up 13.5% at 10:30 GMT.

"The investment provides a solid vote of confidence in the long term value of Ithaca by a successful oil and gas investor," said Ithaca chief executive Les Thomas in a statement.