LONDON— BP PLC has agreed to buy a 10% stake in Eni SpA's super-giant Zohr gas field offshore Egypt, expanding an already extensive footprint in the country. The $375 million stake in the Shorouk concession will give BP access to one of the biggest gas discoveries in recent years. The Zohr field was discovered by Eni in 2015 and is thought to hold roughly 30 trillion cubic feet of gas. The Italian oil company has said it will sell €7 billion in assets by 2019, largely through divesting stakes in recently discovered fields, to help it weather a dramatic crash in oil prices and to finance future developments.