AMMAN (Reuters) - The Syrian army and its allies has taken full control of the Yarmouk Basin in southwestern Syria after routing Islamic State (IS) militants, the Hezbollah group’s al-Manar TV said on Tuesday.

The basin borders Israel and Jordan and had been the last embattled pocket of the southwest after a sustained advance by President Bashar al-Assad’s forces into the longtime rebel stronghold.

The Iranian-backed Hezbollah has fought alongside Assad’s forces as he has turned the tide of the civil war against rebels and militants with the help of Russian air power since 2015.

The army seized Islamic State’s main redoubt in the town of Shajara on Monday, which left just a few villages in the hands of an IS-affiliated faction, the Khalid Ibn al-Walid army, that had controlled the Yarmouk Basin.

The rural area has been the last wedge of southwestern Syria with continued fighting, with the army having taken control of the border with the Israeli-occupied Golan Heights and most of Deraa province to the east.

Between 1,000 and 1,500 IS insurgents who had been holding their ground in the area yielded under intensive Russian bombing from the air, a regional intelligence source said.

Hundreds of air strikes also prompted thousands of civilians to flee and caused untold civilian casualties, according to another Western intelligence source.

Assad is in his strongest position since the early days of the seven-year war that has killed half a million people. Completing his recovery of the southwest would leave rebels largely confined to a stretch of territory in the northwest.