Oil investment in 2016 is likely to decline further after sliding this year by more than a fifth, Fatih Birol, executive director of the International Energy Agency (IEA), said on Monday.

"If it comes true, this will be the first time in two decades we will see oil investments declining for two consecutive years and may be an indication for future oil markets," he said at the Singapore International Energy Week.

There has already been a more than 20 per cent decline in oil investments in 2015, he said, adding that the bulk of the decline in oil investments came from North America and Brazil. – Reuters