Nigeria is expected to lose around 50 percent of its current oil production as strike by workers and attacks by rebels have forced its two biggest oil firms, Exxon Mobil and Royal Dutch Shell, to close its oil production, pushing oil prices near all-time high on Friday.

Exxon Mobil, Nigeria's leading producer, shut down its oil output after a strike by workers over a labor dispute broke out.

Nigerian Minister of State for Energy Henry Odein Ajumogobia met with union leaders today in an attempt to end an oil workers union strike against Exxon Mobil's Nigeria unit.

We are working with the Nigerian government to resolve outstanding issues and to minimize any supply impacts, Exxon said in a statement.

Meanwhile, rebels in the infamous Niger Delta attacked a major Royal Dutch Shell oil pipeline late Thursday, making it the fourth attack this week.

I don't know what's driving this new wave of militancy,'' Ajumogobia said of the attacks. It's one day. We'll take each day as it comes.'' The production losses are temporary, he added.

Ajumogobia said the recent attacks on Shell-run pipelines, including the latest one, is causing oil flows to be reduced by around 140,000 barrels a day, .

The Nigerian supply losses helped push June crude oil futures as high as $119.55 a barrel on the New York Mercantile Exchange.

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