* World needs to invest $38 trillion in oil and gas by 2035
* Up 15 pct on IEA's 2010 estimate
* Lack of investment could raise oil prices in next 5 years (Adds quotes from Eni's CEO, background)
By Muriel Boselli and Sybille de La Hamaide
PARIS, Oct 18 (Reuters) - The Arab Spring has disrupted investment plans in oil and gas projects as some governments in the region have shifted their focus to meet increasing demands from their population, the International Energy Agency said on Tuesday.
As a result, this could in the next five years push oil prices higher, the IEA's chief economist Fatih Birol said at a briefing on the sidelines of the agency's two-day ministerial meeting.
The IEA estimates the world needs to spend $38 trillion to meet projected energy demand up to 2035, up 15 percent from their 2010 forecast of $33 trillion.
World energy ministers and industry leaders started a two-day meeting on Tuesday hosted by the IEA to discuss investment needs with energy-hungry emerging economies.
Birol said there was reluctance from some oil producers to invest enough.
"One of the question mark is over the Middle East and Northern Africa region which is crucial to meet demand growth and to meet decline in the existing production," he said.
"Some countries seem to follow different oil policies not to raise production as much as the market would like to see," he said. "In other countries, they are not able to put money for projects on the table because they have other pressing issues in their countries to meet demands from the population."
"In some countries because of the unrest the projects are not going forward as much as we would like to see," Birol added.
The IEA said 90 percent of the growth in oil production in the next 10 years needs to come from Middle Eastern and North African countries.
In an excerpt from the World Energy Outlook to be published on Nov. 9, the IEA said $10.0 trillion would be needed for oil investments, $16.9 trillion for power, $9.5 trillion for natural gas from 2011 to 2035.
In a speech to the IEA's ministerial delegates, Eni Chief Executive Paolo Scaroni said that while the impact of the Arab Spring on energy security was difficult to assess for now, he had good reasons to be optimistic.
"The first is that the way the crisis evolved in Libya is an exception, rather than the rule," Scaroni said, adding that after months of fighting, Libya had returned to production very quickly. Eni was the largest foreign producer in Libya before the civil war.
Scaroni said his main reason to be optimistic about Middle Eastern and Northern Africa oil supply was Iraq, even though it was still unclear whether it would meet its 12 million barrel per day output target for 2017. (Additional reporting by Tom Bergin and Caroline Jacobs; Editing by Marie Maitre)