More then 50 people have been killed in bomb and mortar attacks in two Syrian cities.
In the besieged city of Homs, a car bomb blast in a mainly Alawite neighborhood killed 36 people. An official said Tuesday's bombing also wounded more than 85 people, most of them civilians.
Meanwhile, in the capital, Damascus, mortar shells killed at least 12 people and injured 50 others in the al-Shaghour section. The Britain-based Syrian Observatory for Human Rights put the death toll at 17.
Syria's government blamed the Damascus attack on "terrorists," a term it uses for the rebels fighting to oust President Bashar al-Assad.
Meanwhile, Human Rights Watch says government forces have continued to use barrel bombs in the northern city of Aleppo, despite a United Nations Security Council resolution demanding a halt to such attacks.
The rights group says that since February, when the council passed the resolution, it has identified the sites of at least 85 bombings in rebel-held parts of Aleppo, with most showing strong signs of impacts left by barrel bombs.
Human Rights Watch is urging the Security Council to impose an arms embargo on the Syrian government and other groups involved in systematic rights abuses.
The group also faults opposition fighters for the use of improvised weapons, saying they are prone to indiscriminate impacts on civilians.
In addition to stopping barrel bombings, the Security Council resolution also demanded that both sides allow aid to reach those in need in Syria. Last week, the heads of U.N. humanitarian agencies said Syria's government and rebels are blocking access to that aid.
A group of 35 international lawyers and legal experts said Monday there is "no legal barrier" stopping the U.N. from carrying out cross-border operations into Syria to help the millions of people who need aid.
In a joint letter published by Britain's Guardian newspaper, the group said such deliveries have been held back by "an overly cautious interpretation of international humanitarian law." The experts urge the U.N. to bring aid into Syria, saying Syria's denial of access has been arbitrary and not for valid legal reasons.
The co-signers include Nicolas Bratza, the former president of the European court of human rights, Hans Corell, a former U.N. under-secretary-general for legal affairs, and Richard Goldstone, who was a chief prosecutor for the U.N. criminal tribunals for the former Yugoslavia and Rwanda.
The U.N. says 3.5 million Syrians are in areas that are under siege or where humanitarian assistance cannot reach them.
The fighting that began in March 2011 has displaced at least 6.5 million people within Syria, with another 2.6 million fleeing to neighboring countries. More than 150,000 people have been killed.