DAMASCUS, June 4 (Xinhua) -- The Syrian army on Saturday entered the administrative borders of the northern province of al-Raqqa, the de facto capital of the Islamic State (IS) group, as jihadist groups in the northern province of Aleppo unleashed a wide-scale offensive against government troops' positions.

The Syrian army backed by Russian air cover managed to cross the administrative borders of al-Raqqa, just days after unleashing a wide-scale offensive on the route between the town of Athriya in Hama province in central Syria, and the al-Tabaqa town in al-Raqqa countryside, according to the Syrian Observatory for Human Rights.

The Syrian forces are trying to reach the al-Furat lake and the road connecting al-Raqqa with the province of Aleppo, said the Observatory, which relies on a network of activists on ground.

Only 40 km separate the army from the targeted areas, said the watchdog group.

The fighting, which broke out on Thursday, has so far killed 26 IS militants and nine security forces.

If the army succeeds, the IS will be besieged by the Syrian army in the south and southwestern parts of Aleppo, while the US-backed Syrian Democratic Forces (SDF) rebels will be besieging the terror group from the west.

The Observatory said the IS police, called Husbah, patrolled the city of al-Raqqa Saturday, threatening to execute anyone who disseminates news about the progress of the Syrian army in al-Raqqa.

It added that the IS is confused now that the Syrian army is advancing from the south and the SDF is advancing in the northern countryside of al-Raqqa and Aleppo.

If the Syrian army controlled the al-Raqqa-Aleppo international road, the IS fighters in Aleppo will be isolated, an achievement that would be in the interest of both the United States and Russia, said the Observatory.

Meanwhile, the al-Qaida-linked Nusra Front, which along with the IS, are both designated by the UN as terrorist groups, which are excluded from any settlements, unleashed an offensive against government troops positions in southern Aleppo and fired tens of improvised rockets on a predominantly-Kurdish district inside Aleppo.

Syria's national TV said over 40 people were killed Saturday by continuous rebel shelling against the Kurdish-dominated Sheikh Maksud district in Aleppo.

The incessant shelling also wounded 100 people, an escalation deemed as a breach to a recently-established and shaky truce, according to the report.

Meanwhile, the TV said 11 other people were killed, including a child, by similar shelling on government-controlled areas in Aleppo city, namely the Masharqa, Midan and al-Faid.

The Syrian Observatory for Human Right said the Saturday's shelling was intense.

Also in Aleppo, the SDF forces are still trying to advance toward the city of Manbej, which is controlled by the Islamic State group, in the northern countryside of Aleppo, near Turkey.

The Syrian army is also engaged in battles against the Nusra and likeminded groups in the southern countryside of Aleppo, mainly near the town of Khan Tuman.

The intensified battles in Aleppo also hit a new high when 1,000 fighters with the Nusra and likeminded groups mounted an offensive against Syrian military positions in southern Aleppo.

Aleppo, Syria's second largest city and once an economic hub, holds its significance due to its location near the Turkish borders. Each party of the conflict is now fighting to consolidate positions, and claim more territory in that key area.

The progress by the Russian-backed Syrian army and the U.S.-backed SDF reflects a US-Russian understanding on the need to isolate IS and weaken its abilities, analysts said.