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 in the second city, Aleppo.
Activists estimate some 20,000 people have died since March last year.
A video has been circulated online showing the execution by rebel gunmen in Aleppo of four men said to be Assad loyalists from the Berri clan. The act was condemned from human rights activists.
In Aleppo, state media said government troops had inflicted heavy losses on the rebels and were mopping up remnants of terrorist groups.
The UN confirmed that their observers had seen fighter jets firing on rebels in Aleppo on Tuesday.
However, activists and reporters on the ground said rebels appeared to still have control over large parts of the city.
A spokesman for the rebels has denied a report on the US channel NBC that they have acquired surface-to-air (Sam) missiles from Turkey.
Mr Assad has not spoken in public for two weeks, but in his written statement, he said: "The fate of our people and our nation, past, present and future, depends on this battle."
He praised the armed forces as "heroic" and described them as the defender of "just causes".
The statement was published in an army magazine and reported by state news agency Sana.
Amnesty International says that government forces committed crimes against humanity this month in 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 the video which appeared on YouTube, gunmen lead a number of men in their underwear, some of them bruised or bloodied, into a yard crowded with men shouting religious slogans.
After the half-naked men are put up against a wall, the camera moves back behind the crowd, losing sight of them. Heavy, sustained gunfire from Kalashnikov assault rifles erupts after which the camera shows a pile of bodies by the wall.
Rami Abdel Rahman, head of the UK-based Syrian Observatory for Human Rights, said of the footage: "This is criminal. This is revenge."
In another development, reports suggested fighting had broken out for the first time near a Christian area of the Old City of Damascus.
Activists reported an outbreak of shooting early on Wednesday morning near the Damascus Christian district of Bab Tuma. There were no immediate further details.
According to the NBC report from northern Syria, the rebel Free Syria Army (FSA) in Aleppo has obtained nearly two dozen shoulder-launched Sam missiles.
However, FSA political adviser Bassam al-Dada told pan-Arabic TV channel al-Arabiya they had "not obtained any such weapons at all".
"Had we acquired such weapons, we would have seen the difference on the ground," he added, speaking by phone from Istanbul.