* Two earthquakes near volcano overnight
* Quakes strike in same range as subglacial eruption
* Iceland on high alert, some airspace closed
* 2010 eruption in Iceland immobilised aviation industry
REYKJAVIK, Aug 24 (Reuters) - Iceland's Met Office said on Sunday two earthquakes had shaken the Bardarbunga volcano overnight, hours after an eruption under a nearby glacier made authorities raise its warning code for the aviation industry to red, signalling possible major disruptions.
Ash from the eruption of Iceland's Eyjafjallajokull volcano in 2010 shut down much of Europe's airspace for six days, affecting more than 10 million people and costing $1.7 billion.
Saturday's small subglacial eruption, which closed part of Iceland's airspace though its airports remain open, was also in the Bardarbunga range, but at a distance of 25 km (15.5 miles) from the earthquakes' epicentres, the Met Office said.
There have been thousands of small earthquakes over the past week at Bardarbunga, which is Iceland's largest volcanic system and located under the ice cap of a glacier. It is in a different range to Eyjafjallajokull, which erupted in 2010.
The Met Office said in a statement a magnitude 5.3 earthquake at 5 kilometers (3 miles) depth had struck after midnight while another, with a magnitude of about 5, had occurred some five hours later.
"These are the strongest events measured since the onset of the seismic crisis at Bardarbunga and the strongest since 1996," the office said on its website.
There was no sign of any eruption at Bardarbunga, it said.
"Probably, earthquakes near the Bardarbunga caldera are a consequence of adjustment to changes in pressure because of the flow of magma from under the caldera into the dyke which stretches to Dyngjujokull."
The region of the Bardarbunga volcano, in the centre of the North Atlantic island nation, has already been evacuated due to days of heightened seismic activity there.
The evacuated zone was extended somewhat on Saturday, but Icelandic airports remain open though airspace of 140 by 100 nautical miles above the volcano has been closed.
The red alert is the highest warning on the country's five-point scale and indicates an eruption is imminent or underway with a significant emission of ash likely. The colour codes are intended to inform the aviation sector about a volcano's status.
Brussels-based aviation authority Eurocontrol said that as soon as the volcano had erupted, the Volcanic Ash Advisory Centre in London would produce a regular forecast about the levels of volcanic ash in the atmosphere. (Reporting by Robert Robertsson; Writing by Niklas Pollard; Editing by Raissa Kasolowsky)