Battle for Damascus

Widespread fighting was reported Thursday across Syria, with at least 21 Republican Guards killed in an explosion in a Damascus suburb where government troops have been battling rebels, according to the Syrian Observatory for Human Rights.

The explosion occurred at a military housing unit in the Syrian capital city's suburb of Qudsaya, the rights group said.

Fierce clashes were also reported in Yarmouk Camp, home to the largest Palestinian community in Syria, the LCC said.

Yarmouk Camp has been the scene of on-again, off-again intense fighting in recent months, with government forces shelling rebels and firing on them from helicopters, according to opposition reports.

CNN is unable to independently confirm reports of casualties or violence because the Syrian government has severely restricted access by international journalists.

The Local Coordination Committees of Syria said Thursday's death toll across the country stood at 72, with 31 dead in Damascus and its suburbs and 26 of those killed in Aleppo. The Republican Guard deaths were not part of the group's count.

Russia: Terror tactics in Aleppo "immoral"

Russia denounced a wave of explosions that left dozens dead in the flashpoint city of Aleppo, Syria's largest city, as "immoral" and "inadmissible."

The comments by the Russian Foreign Ministry came as the al Qaeda-linked al-Nusra Front claimed responsibility for Wednesday's bombings that killed at least 40 people and wounded 90 more. The group said the strikes at a popular square were carried out by suicide bombers who drove explosives-laden vehicles and by gunmen disguised as Syrian security forces.

The seesaw fight for Aleppo, once considered an al-Assad stronghold, has continued nearly unabated since July, though the number of casualties has steadily increased.

"Those behind the attacks and those who carried them out must be found and punished," the Foreign Ministry said in a post on its official Twitter account. "Supporting those who commit crimes like these is immoral and inadmissible."

Russia, along with China, has repeatedly blocked U.N. Security Council efforts to try to end the carnage. Russia's Foreign Ministry has said the conflict must be decided by the Syrian people.

While most of the Western members of the Security Council condemned the border attack, Lavrov, the Russian foreign minister, had sharp words for the council's failure to condemn the attack in Aleppo.

He said he regrets the "Security Council once again failed to condemn terror acts in Syria."

Lavrov also said Damascus should promise publicly to prevent armed incidents on the border with Turkey.