Heavy air strikes hit rebel-held east Aleppo in the early hours of Monday, days after the United States and Russia announced plans to reinforce the February 27 truce in Latakia and Damascus regions.
Ban is "profoundly concerned about the dangerous escalation of fighting in and around Aleppo and the intolerable suffering, counted in mounting deaths and destruction, it is causing among civilians," said UN spokesman Stephane Dujarric.
The appeal came on the eve of talks between Ban's envoy for Syria, Staffan de Mistura, and Russian Foreign Minister Sergei Lavrov in Moscow on the collapsing ceasefire.
He called on all international actors, in particular the United States and Russia "to redouble their efforts in support of the Syrian parties to put the cessation of hostilities back on track."
"The collapse of the cessation of hostilities will only bring more violence, death and destruction while further weakening efforts to find a negotiated solution to this brutal war," said Ban's spokesman.