UPDATE 1-Syrian rebels capture eastern town of al-Shaddadeh -sources

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AMMAN, Feb 14 (Reuters) - Syrian rebels seized a town in an eastern oil-producing province on Thursday after three days of heavy fighting in which 30 Nusra Front fighters and 100 Syrian troops were killed, a violence monitoring group said.

Taking Shaddadeh in Hasakah province from the forces of President Bashar al-Assad brings the rebels closer to the provincial capital Hasakah, 45 km (30 miles) to the north.

Coinciding with the report by the Syrian Observatory for Human Rights on the fighting was a video posted on YouTube showing fighters from the al Qaeda-linked Nusra Front celebrating and chanting "Allahu Akbar (God is Greatest), Nusra Nusra".

Omar Abu Laila, a spokesman for the eastern command of the rebel Free Syrian Army, said rebel units including Nusra fighters now controlled al-Shaddadeh after overrunning state security and military intelligence compounds.

Hasaka, an ethnically mixed province of Arabs and Kurds, accounts for most of Syria's oil output, which is estimated to have fallen by a third to no more than 100,000 barrels per day since an uprising against Assad's rule erupted in March 2011.

Abu Laila said an army garrison guarding a nearby gas field, al-Ghabsa, had fled as armed opposition units advanced from the Euphrates River toward Shaddadeh. (Reporting by Khaled Yacoub Oweis, Amman newsroom; Editing by Mark Heinrich)