Syrian President Bashar al-Assad has said that the army's battle with rebel forces would determine the fate of his country, and praised soldiers for confronting what he said were "criminal terrorist gangs".
"The fate of our people and our nation, past, present and future, depends on this battle," Assad, who has not spoken in public for two weeks, said in a written statement marking armed forces day on Wednesday.
Assad said the army was waging a "heroic" battle against the enemy and the country was engaged in a "crucial battle for its destiny". Earlier on Wednesday, fierce fighting between the rebels and the army erupted near two Christian areas of central Damascus for the first time in the nearly 17-month uprising, as the battle for Aleppo continued into its 12th day.
Also on Wednesday, the United Nations mission in Syria says its observers have witnessed government fighter jets opening fire on Aleppo, the country's largest city.
In a briefing on Wednesday, mission spokeswoman Sausan Ghosheh also said the UN had confirmation that the rebels now have heavy weapons of their own, including tanks.
Ghosheh expressed concern over the situation in the northern city of Aleppo, where rebels have been battling government forces for the past 12 days. She described "heavy use of heavy weapons, including tanks, helicopters, heavy machine guns, as well as artillery".
In fighting across other parts of the country, at least one government soldier was killed in clashes in Damascus' Bab Tuma and Bab Sharqi districts, the Syrian Observatory for Human Rights, the UK-based activist group, said.
"This is fighting in areas where it has not happened before. These are areas where the rebels have so far not had access," Observatory chief Rami Abdel Rahman told the AFP news agency.
Bab Tuma and Bab Sharqi in the Old City of Damascus were previously popular with tourists and were the scene of several pro-regime protests in the past.
Furthermore, the Local Co-ordination Committees (LCC), which organises protests on the ground, reported a blast and heavy gunfire from Baghdad Street, a main route in Syria's capital. The LCC also said that the capital's southern suburb of Tadamun was hit by mortar fire at dawn.