Syrian activists are reporting continued deadly shelling by government forces, a day after U.N. Secretary-General Ban Ki-moon expressed concern about the ongoing aerial and artillery attacks.

Activists said shelling in the Damascus suburb Douma killed two people Tuesday, and that government forces blasted other rebel strongholds outside the capital.

The Local Coordination Committees said attacks also took place in Daraa and Idlib.

A U.N. spokesman Monday said Mr. Ban appealed to Syrian Foreign Minister Walid al-Moualem for the government to “show compassion to its own people.” The two met on the sidelines of the U.N. General Assembly in New York.

During a speech to the General Assembly, Moualem accused the United States, France, Qatar, Saudi Arabia and Turkey of supporting “terrorism” in Syria by providing arms and money to rebels. He also characterized calls for Syrian President Bashar al-Assad to step down as “blatant interference” in Syrian domestic affairs.

Syria's state-run SANA news agency said Tuesday the military killed a group of terrorists and destroyed “explosives factories” in Aleppo.

On Monday, fires broke out in more parts of Aleppo's medieval Old City as rebels and government forces engaged in fierce fighting.

The fires began in the Old City's medieval Souk al-Medina, a vast covered market, on Saturday, damaging hundreds of shops selling fabrics, perfumes and spices. Traders and visitors to the city described the fires as a side effect of the clashes in the souk.

UNESCO designated Aleppo's Old City as a World Heritage Site in 1986. UNESCO Director-General Irinia Bokova said the Syrian conflict is “destroying cultural heritage that bears witness to the country's millinery history, valued and admired the world over.”

She said Syria is obliged to safeguard its heritage from war as a signatory to the 1954 Hague Convention for the Protection of Cultural Property in the Event of Armed Conflict.

The Damascus representative of the new international envoy for Syria said the large number of deeply divided rebel groups is one of the main obstacles to the U.N. mission's efforts to end the country's prolonged crisis.

Mokhtar Lamani, who represents special envoy Lakhdar Brahimi in the Syrian capital, also pointed to “huge fragmentation” within Syrian society, which he said contributes to a high level of mistrust. He said “many elements that have nothing to do with Syria” are taking advantage of the situation.