A group of military defectors known as the Free Syrian Army have said they plan to overthrow President Bashar Assad's "murderous" regime.
The group's leader Riad al-Asaad, an air force colonel who recently fled to Turkey, said the group now has more than 10,000 members and called on fellow soldiers to join him.
He said: "They will soon discover that armed rebellion is the only way to break the Syrian regime.
"I call on all the honourable people in the Syrian army to join us so we can liberate our country. It is the only way to get rid of this murderous regime."
The trend towards a militarisation of the uprising has raised fears that Syria may be sliding towards civil war.
Shadi Hamid, director of research at the Brookings Doha Centre in Qatar, said: "The Libyan model is looking increasingly attractive to the Syrian opposition."
However, he described the dissident army as a "high-risk, high-reward situation".
He said territorial gains might encourage the international community to offer support and make regime change more real in the minds of outside observers.
"But the flip side of that is that it gives the regime... pretext to wipe out a city so it is a very risky move," Hamid added.
Nearly 3,000 people have been killed in the violence since March, according to the UN and activists.