Free Syrian Army fighters pose on a tank (Reuters)

Syrian rebels are building on their recent momentum in the civil war after seizing a second key army base near the Iraqi border.

The fall of the Mayadeen military base, on the River Euphrates, is the latest in a series of strategically important victories rebels have scored against the regime of Bashar al-Assad.

"The whole countryside, from the Iraqi border and along the Euphrates to the city of Deir al-Zor, is now under rebel control," Abu Laila, an official in the Military Revolutionary Council in the province, said.

He added that 44 rebel fighters had died in the Mayadeen operation.

Earlier in November, Free Syrian Army rebels conquered the city of al-Bukamal and sacked a major airbase in the area.

Their success reportedly gave rebels the upper hand in the province. They claimed that they were in control of the 125km of road connecting the city of Deir al-Zor to Iraq, Reuters reported.

In another important victory, Syrian rebels conquered a large military base in the north of the country after a 50-day siege.

The Syrian Army's 46th Regiment's base about 25km (15 miles) west of Aleppo, was taken earlier this month, and so were its precious stocks of weapons.

Tanks, armoured vehicles and truckloads of munitions were commandeered by the FSA.

"There has never been a battle before with this much booty," Gen Ahmad al-Faj of the rebels' joint command said.

Meanwhile, the new coalition of groups opposed to Syrian President Bashar al-Assad - the National Coalition of the Syrian Revolutionary and Opposition Forces - is making important steps at diplomatic level in gaining international recognition.

UK foreign secretary William Hague followed France, Turkey and six Gulf states in calling the alliance "the sole legitimate representative" of the country's people.