Royal Dutch Shell (RDS.A, RDSA.L), the world’s second-largest listed oil and gas company, reported early Thursday a drop in adjusted earnings as “challenging” macroeconomic conditions in refining and lower gas prices hit revenue in the second quarter.

Sales fell to $90.54 billion during the three months that ended June 30, from $96.77 billion a year ago, the Anglo-Dutch company said in its earnings statement. Group turnover beat the $90.12 billion average analyst estimate from Capital IQ.

Shell’s preferred measure of adjusted income per share, the current cost of supplies earnings per basic share excluding identified items, came in at $0.43 from $0.56 a year earlier.

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The company said lower earnings reflected lower realized oil, gas and liquified natural gas prices, weaker realized chemicals and refining margins, as well as higher provisions, partly offset by improved overall production. Integrated Gas was hit particularly hard as lower output and prices undermined the unit’s earnings.

In a separate statement, Shell announced the start of the next tranche of its share buyback program under which the firm will repurchase $2.75 billion of Class A/B ordinary shares for a period up to October 28. Since the launch of the program, almost 294 million Class A ordinary shares have been bought back for cancellation for $9.25 billion.

The group also set out a $0.47 interim dividend for the second quarter, unchanged sequentially from the previous three months as well as a year ago and payable on September 23.