UN Security to hold urgent meeting on Syria

After a weeklong truce, war has raged n Aleppo where nearly 300,000 civilians are besieged and in desperate need of humanitarian assistance.

Secretary-General Ban Ki-moon is "appalled by the chilling military escalation in the city of Aleppo, which is facing the most sustained and intense bombardment since the start of the Syrian conflict," a statement from the UN said.

The Syrian regime announced Thursday an offensive against the country's pre-war second city and reports have since surfaced of airstrikes involving the use of incendiary weapons and advanced munitions such as bunker buster bombs.

"The apparent systematic use of these types of indiscriminate weapons in densely populated areas may amount to war crimes," the statement added.

Describing the reported attacks as a "dark day" for the global commitment to protect civilians, Ban called on the international community to "unite to send a clear message" of no tolerance for the use of deadly weapons against civilians.

In a joint statement Saturday, the foreign ministers of France, Germany, Italy, U.K., U.S. and the EU foreign policy chief said the campaign in Aleppo "blatantly contradicts Russia’s claim that it supports a diplomatic resolution.

"The Quint nations and the European Union High Representative therefore call on Russia to take extraordinary steps to restore the credibility of our efforts, including by halting the indiscriminate bombing by the Syrian regime of its own people, which has continually and egregiously undermined efforts to end this war," the statement said.

The regime's offensive came days after a truce ended catastrophically after a UN aid convoy was bombed before reaching Aleppo to deliver aid.

The regime vehemently protested an attack on its troops early last week when a U.S. airstrike hit a regime unit and killed 62 soldiers.