DAMASCUS, June 9 (Xinhua) -- Jihadist militant groups on Tuesday unleashed a wide-scale offensive on a key Syrian military base in the southern province of Daraa, killing 20 government soldiers, a monitoring group reported.

The militants launched their attack against the Brigade 52, one of the major military bases in Daraa province and managed to capture large parts of it, according to the Syrian Observatory for Human Rights.

The UK-based watchdog group said the Islamist militants announced the battle to capture the base and several towns in the northern countryside of Daraa. They also stormed the towns of Rakham, and Western Mlaiha.

The possible downfall of the entire base would pose threat to the nearby airbase of Thaleh in the province of Swaida, which is largely inhabited by pro-government Syrians.

Meanwhile, the so-called Southern Front Formation, one of the various rebel groups, said the entire base has fallen.

For its side, the Syrian official TV said the Syrian army repelled an attack against a military base in northeastern Daraa, spelling no further details.

Several jihadist groups have recently been expanding their control in Daraa, the birthplace of the Syrian crisis.