The conflict between rebels and government forces across Syria will decide the fate of the nation, President Bashar al-Assad has warned.
In a written statement marking armed forces day, he praised soldiers for confronting “armed terrorist gangs”.
The anti-regime uprising has in recent weeks seen fighting on the streets of the capital Damascus and the second city Aleppo.
Activists estimate some 20,000 people have died since March last year.
The latest reports suggest fighting has broken out for the first time near two Christian areas in the Old City of Damascus.
One soldier had been killed outside Bab Touma and Bab Sharqi, the UK-based Syrian Observatory for Human Rights said.
Gunfire and explosions were also heard on Baghdad Street, in the city centre.
Mr Assad has not spoken in public for two weeks, but issued a statement to mark armed forces day.
“The fate of our people and our nation, past, present and future, depends on this battle,” the statement said.
He praised the armed forces as “heroic” and described them as the defender of “just causes” in the statement, which was published in an army magazine and by the state news agency Sana.
Meanwhile, Amnesty International says in a report that government forces committed crimes against humanity this month in the second city, Aleppo.
In the report, based on research carried out in May, the rights group appealed to the UN Security Council to refer Syria to the International Criminal Court and impose an arms embargo on the country.
Amnesty accuses security forces and pro-government militiamen, known as shabiha, of firing on peaceful protesters and bystanders, including children. It also says medical teams were targeted and those arrested were often tortured.
In Aleppo itself, rebel sources say fighter jets and helicopters have again been pounding rebel positions as the battle for control of the city continues.
Activists have also told the BBC that a large military column is heading towards Aleppo to reinforce the army units engaging the rebels. However, this has not been confirmed by the government or independent sources.