By Selina Williams

LONDON--U.K.-listed Tullow Oil PLC (TLW.LN) said Wednesday that it has encountered oil at its Twiga South-1 exploration well in its onshore Kenya block--news that could help advance the company's ambitious plans for the region.

Drilling is on-going and a further announcement of the drilling results is expected in early to mid-November after the target depth has been reached and necessary sampling and analysis has been completed, the company said in a statement.

The Twiga South-1 structure is the second prospect to be tested as part of a multi-well drilling campaign in Kenya and Ethiopia and is the first discovery in Block 13T following the Ngamia-1 discovery earlier this year in Block 10BB.

The U.K. independent oil and gas explorer has big ambitions for the region, including potential plans for pipelines to transport crude from Uganda and Kenya, underscoring East Africa's potential to become a major new exporter of energy later this decade.

In addition to the oil already found in Uganda and Kenya, major gas discoveries have been made in their southern neighbors Tanzania and Mozambique.

Tullow has a 50% stake in the Twiga South-1 well with Africa Oil holding the remaining 50% interest.

At 1120 GMT, Tullow was trading up 3% at 1,424 pence per share, outperforming the broader FTSE-100 index, of which it is a component.

Write to Selina Williams at selina.williams@wsj.com

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