BEIJING - UN Secretary-General Ban Ki-moon said on Thursday he was alarmed by the intensifying violence in Syria, saying he "strongly condemns" the bombing in Damascus that killed the Syrian defence minister and President Bashar al-Assad's brother-in-law.

Ban "is also gravely concerned about reports of the continued use of heavy weapons by the Syrian security forces, including in the Damascus area, against civilians, despite repeated government asssurances that such weapons would be withdrawn," the United Nations said in an emailed statement.

Ban, who is on a three-day visit to China, urged members of the Security Council to take collective and effective action in view of the escalating situation in Syria.

"Time is of the essence," Ban said. "The Syrian people have suffered for too long. The bloodshed must end now."