Terrorist militants have fired a barrage of mortars and rockets into a busy market in the northern Syrian city of Aleppo, leaving at least 14 people dead and 40 more injured. State-run news agency SANA said on Sunday the attack by "terrorists" occurred in the Kurdish-dominated neighborhood of Sheikh Maqsoud, which has been targeted by shelling despite a US and Russian-brokered ceasefire that took effect February 27. The so-called Syrian Observatory for Human Rights, a Britain-based opposition group that monitors the conflict, said more than 70 rockets and mortar shells were fired at Sheikh Maqsoud. The Observatory said the shells were fired by militants, affiliated with the al-Qaida-linked al-Nusra Front, Ahrar al-Sham Salafist movement with close ties to Turkey, and Daesh. Kurdish fighters from the Kurdish People’s Protection Units (YPG) have been engaged in heavy fighting with anti-Damascus militants in recent months. Turkey has been slammed for supporting anti-Damascus militants with funds, training and weapons. The ceasefire has caused a sharp drop in violence in much of Syria and has largely held despite sporadic violations and mutual accusations of breaches. The US and Russia are now looking to convince the two sides to return to UN-brokered peace negotiations in Geneva next week. In a telephone conversation Sunday, Russian Foreign Minister Sergey Lavrov and US Secretary of State John Kerry gave "an overall positive assessment of the progress toward securing the ceasefire in Syria, which is being generally observed and already has led to a sharp decrease in the level of violence," the Russian Foreign Ministry said in a statement. Although much less aid than anticipated has gone into besieged areas since the ceasefire started, the diplomats noted "significant improvement" in humanitarian access. They stressed the need to avoid delaying the start of the Geneva negotiations.