APphoto_Mideast Syria

This image provided by Aleppo Media Center, which has been authenticated based on its contents and other Associated Press reporting, shows Syrians inspecting a burnt bus after a missile fired by government aircraft hit the vehicle Tuesday in Aleppo. On Wednesday, a missile reportedly fired by government forces hit a residential building in the city, killing at least 20 people. (Handout / Associated Press / December 31, 2013)

AMMAN, Jordan -- At least 20 people were killed in Aleppo on Wednesday when a residential building was hit with a rocket from a warplane as the government’s daily bombardment of the northern Syria city continued, activists said.

More than 500 people have been killed across Aleppo province in two weeks of a fierce government offensive with rockets and destructive barrel bombs, local doctors and human rights groups reported.

World leaders have called for an end to the attacks, which have put into question the upcoming Geneva II peace conference. The main political opposition group, the Syrian National Coalition, has said it will boycott the talks if the bombing didn’t end.

“You can’t imagine these tools of death,” said Khalid Omar, a member of the Union of Free Medicine in Aleppo.

Syrian forces launched mortar shells Wednesday onto a border village in Lebanon, and wounded 10 Syrian refugees, one critically, Lebanese state media reported. Abu Hamzeh, a rebel fighter in nearby Arsal, said the mortar rounds struck two cars carrying refugees, killing a woman and her child.

On Monday, the Lebanese army fired on Syrian government aircraft that officials said had launched missiles at the same border village, Khirbet Dawood. It marked the first military response by Lebanon to occasional Syrian shelling and attacks.

Arsal, a Sunni Muslim town in a mostly Shiite Muslim area, has hosted thousands of Syrian refugees who continue to stream across the border and has come under attack on previous occasions.

Now approaching the end of its third year, the conflict in Syria has left more than 130,000 dead, reported the Syrian Observatory for Human Rights, a pro-opposition rights group, this week. Nearly 12,000 of those were women and children.

As the violence on the ground continued, the Syrian government of President Bashar Assad missed the end-of-year deadline for the handover of its chemical weapons, a result of ongoing clashes, inclement weather and logistical issues.

The Tuesday deadline was to have been the first milestone in an agreement to strip Syria of its chemical arsenal by mid-2014.

Syria agreed to give up its chemical weapon stockpiles after widespread condemnation of a sarin gas attack allegedly carried out Aug. 21 by government forces on rebel-held areas outside of Damascus. Assad denied involvement in the attack, which reportedly killed hundreds of people and brought the U.S. to the brink of launching airstrikes against Syrian forces.

Norwegian and Danish navy ships had left Cyprus early this week to wait off the Syrian coastal city of Latakia, where Damascus had promised to deliver part of its chemical weapons stockpile to be transported for destruction on Tuesday. By noon Monday, they had returned to Cyprus.

Nevertheless, the United Nations' disarmament body lauded the progress that had been made while calling on all parties to "intensify efforts.”

Sigrid Kaag, special coordinator for the United Nations and the Organization for the Prohibition of Chemical Weapons, remained optimistic, saying "that continued solid progress has been achieved" while stressing that "at the end of the day, failure is not an option, success is within reach.”

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Twitter: @rajaabdulrahim

raja.abdulrahim@latimes.com

Special correspondent Bulos reported from Amman and Times staff writer Abdulrahim from Panama City, Fla.