Islamic State fighters have recaptured Ain Issa, a key Syrian city near a supply route, from Kurdish forces, while a group linked to ISIS claimed responsibility for a rocket attack that hit southern Israel on Friday, reports said.

Kurdish forces took control of the city and Tal Abyad last month with help from US-led coalition airstrikes, the London-based Syrian Observatory for Human Rights said.

Both Ain Issa and Tal Abyad are strategically crucial as they are located along a supply route on a road going to Raqqa, considered as the de facto capital of what ISIS claimed as its caliphate, a CNN report said.

The recapture of Ain Issa by the extremist group comes after a weekend of airstrikes on ISIS targets in Raqqa, which were "the most sustained set of airstrikes to date" against the jihadists in Syria, said Brett McGurk, the US envoy for the coalition against ISIS.

In another development, a ISIS-affiliate based on Sinai claimed responsibility for the three Grad-style rockets fired at southern Israel on Friday, CBN News reported.

No one was injured by the attack by the terror group Wilayat Sinai (Sinai Province), previously known as Ansar Beit al-Maqdis. No property was damaged.

Prime Minister Benjamin Netanyahu again aired his support for the campaign against ISIS, which he described as "our common enemy and that of humanity as well."

"We are monitoring all the events and are taking all necessary measures," Netanyahu told his cabinet, noting the latest round of attacks across Israel's southern border reinforces the importance of the security fence, which "prevents, or renders very difficult, ground infiltrations by ISIS and other terrorist elements."

Israel also strengthened its northern border with war-torn Syria, where ISIS-linked extremists fire rockets on the Golan Heights from time to time.

"We built a similar fence on the Golan Heights against ISIS and other terrorist elements there, and, as you know, we have also started to build a security fence on our eastern border," Netanyahu said.