Royal Dutch Shell on Thursday said it plans to reduce its headcount by 6,500 this year owing to sliding oil prices and as it looks to complete a mega takeover.

"Today's oil price downturn could last for several years, and Shell's planning assumptions reflect today's market realities," the company said in a statement, adding that it anticipates "some 6,500 staff and direct contractor reductions in 2015".

Shell earlier this year unveiled a mega-takeover of British rival BG Group worth £47 billion ($73 billion, 67 billion euros), as the two firms consolidate their positions in a sector slammed by the oil price slump.