Damascus, October 9 (RHC)-- A huge car bomb targeting areas just outside the northwestern Syrian city of Aleppo has killed at least 20 people. Security sources said on Thursday that tens of people were also injured in the blast in the Hraytan town, about five kilometers north of Aleppo.

No group has claimed responsibility for the attack; however, the area has been frequently targeted by various militants groups operating in northern Syria.

Thursday's attack may have been a response by the militants to a joint air campaign by Russia and Syria, which has reportedly forced militants to leave some of their key positions in the area.

Military officials announced earlier in the day the launch of a large-scale operation against the strongholds of militants in the Aleppo Province, following heavy air raids by Russian and Syrian air forces.

“Today the Syrian armed forces started a wide-scale attack aiming at uprooting terrorists’ gatherings and liberating the areas and towns which have been suffering the woes and crimes of terrorism,” Chief of the General Staff of the Syrian Armed Forces General Ali Abdullah Ayoub said.

For more than four years, Syria has been grappling with a deadly militancy which it blames on some foreign countries, including its northern neighbor, Turkey. Around 250,000 people have lost their lives and millions more have been displaced.