U.N. Secretary-General Ban Ki-moon is painting a worsening picture of the war in Syria, citing indiscriminate government bombing and opposition shelling, high civilian casualties and deteriorating humanitarian conditions.

In his monthly report to the U.N. Security Council obtained Friday by The Associated Press, the Ban said the use of roadside and vehicle-borne improvised explosive devices increased and more than 21 suicide operations were reported in the provinces of Aleppo, Hama and Daraa in December.

He said fighters from the Islamic State terrorist group, who control about one-third of Syria, reportedly incurred heavy casualties in intensified fighting with Kurdish forces last month. He said the al-Qaida-linked Nusra Front reportedly continued to attract additional fighters and resources, particularly in Idlib and Daraa.