DAMASCUS, Dec. 6 -- Intensified air strikes targeted positions of the Islamic State (IS) on Sunday in Syria, killing and wounding tens of IS militants, activists and local media said, as President Bashar al-Assad slammed the French and British anti-terror efforts as lacking the will and vision to defeat IS.

Warplanes, believed to be Russian, carried out over 45 air strikes on the IS positions in the ancient city of Palmyra in central Syria, leaving unknown number of causalities, according to the Syrian Observatory for Human Rights.

The UK-based watchdog group said the air strikes were coupled with ground battles between Syrian troops and IS terrorists near Palmyra, which was stormed by IS last May in the eastern countryside of Homs province in central Syria.

In the IS de facto capital of al-Raqqa in northern Syria, a total of 70 IS militants were either killed or wounded when warplanes, believed to belong to the U.S.-led anti-terror coalition, struck their positions in northern and eastern al-Raqqa, according to the Observatory.

It said 15 powerful explosions, caused by air strikes, rocked positions of IS in al-Raqqa.

The Observatory added that Syrian air strikes against rebel positions in the eastern countryside of the capital Damascus killed at least 13 people on Sunday.

Meanwhile, the official SANA news agency said Syrian forces backed by Russian air strikes killed at least 55 IS militants and jihadists with the so-called Conquer Army in separate military operations in the countryside of the central province of Hama and the northwestern province of Idlib.

The air strikes against IS have increased after the deadly attacks in Paris last month, where over 120 people were killed when attackers went on a rampage in several districts.

After the attacks, which were claimed by IS, Paris intensified air strikes on IS positions in Syria. And Britain has recently joined the U.S.-led anti-terror coalition to pound IS in Syria. Germany has later said it will also expand the fight against IS in Syria.

Syria officials repeatedly hailed the Russian air strikes as effective, while expressing skepticism over the U.S.-led coalition, particularly the recent French and British involvement.

In his recent interview with the British Sunday Times, President Bashar al-Assad said "we know from the very beginning that Britain and France were the spearheads in supporting the terrorists in Syria, from the very beginning of the conflict."

The president stressed that "It is legal only when the participation is in cooperation with the legitimate government in Syria. So, I would say they (French and British) don't have the will and they don't have the vision on how to defeat terrorism."

Assad said since the U.S. coalition started its operation a year ago, the terrorist groups such as IS and the al-Qaida-linked Nusra Front have expanded freely, adding that after the Russian air strikes two months ago, the sway of the terrorist groups started to shrink.

"This kind of operation (French and British strikes) is like cutting the cancer that will make it spread in the body faster," Assad said.