The Kurds in Hasaka have a large community in the northern and northwestern parts of that city while the government troops hold positions in the southern part of Hasaka.
The Ekhbarieh TV said Kurdish fighters of the People's Protection Units are monitoring the battles in southern Hasaka without intervening.
Earlier this week, the IS staged several car bombings in Hasaka,
leaving dozens of people wounded or killed. The attack on Hasaka on Thursday has been the second in June.
The last attack was foiled by government forces, and the Kurdish fighters said then also that they would not interfere in the battles.
Abdul-Karim Sorkhan, a Kurdish leader, said both the Syrian forces and IS are antagonist to the Kurds, and that the Kurdish fighters are on standby to protect the densely Kurdish populated areas in the northern and western parts of the city.
In another escalation Thursday, a coalition of 51 rebel and jihadi groups declared the start of a major offensive to drive government forces out of the southern province of Daraa.
The offensive, dubbed "the Storm of the South," aims to take control of the entire city of Daraa and its vicinity, according to the Observatory.
Intense battles have been raging since Thursday morning in Daraa between government forces and an array of jihadist groups, which targeted government positions with mortars and heavy machine guns near the town of Atman in the countryside of Daraa, according to the Observatory, which says it relies on a network of activists on the ground inside Syria.