Erdogan, who is visiting Libya, told a cheering crowd in Tripoli's Martyrs' Square, formerly Green Square, that by ousting Muammar Qaddafi the Libyan people had set an example to others seeking to throw off oppression.
"You are the ones who showed the whole world that no administration can stand in the way of the might and will of the people," Erdogan said, as people chanted "Turkey, Turkey."
"Do not forget this: those in Syria who inflict repression on the people will not be able to stand on their feet because oppression and prosperity cannot exist together," the prime minister said.
Erdogan was ending a North African tour in Libya, where he hopes to reap political and economic dividends from its new rulers for Turkey's help in their struggle against Qaddafi.
His visit came a day after French President Nicolas Sarkozy and British Prime Minister David Cameron were received as heroes in the Libyan capital. French and British air power had helped rebels overrun Tripoli forcing Qaddafi to flee.
Erdogan, who had already received a rapturous welcome in Egypt and Tunisia, was greeted by crowds of people in the same square where Qaddafi delivered some of his fiercest speeches to rally support against the rebellion.
Erdogan attended Friday prayers in the square alongside hundreds of people and the chairman of Libya's National Transitional Council (NTC) Mustafa Abdel Jalil.
"They hesitated at first to support the revolution, but after he (Erdogan) saw there was support for the revolution from the Libyan masses, he stood by the people," said computer engineer Abdulsalaam Mohammed, who had waited for an hour to enter the square with his five-year-old son.
"There's no comparison, he is cleaner than any Arab leader."
Erdogan said the age of autocracies and totalitarian regimes was over. "Now, the power of the people is coming and I congratulate you on your struggle," he said.
Having repeatedly urged Assad to end a crackdown on protesters and launch meaningful reforms, Erdogan has become increasingly critical of the Syrian leader, while stopping short of calling for his departure.
At a news conference later , Erdogan said Turkey's approach to Syria had changed and that Ankara would soon announce its "final" decision on Syria by the time the UN General Assembly meeting in New York next week. "Our approach now to Bashar is not the same as the approach we had one to two months ago," Erdogan said.
Syrian forces meanwhile shot dead 20 people on Friday and flooded rural areas around Damascus with troops to try to end six months of demonstrations against Assad.
Despite the heavy deployment, activists reported protests on the edges of the capital, the northern province of Idlib bordering Turkey and other parts of Syria. Banners proclaimed protesters were "on course to bring down the regime."
After storming several cities in August to crush protest centers, the Syrian Army has swept through rural districts in recent weeks, hunting down activists and army defectors, carrying out widespread arrests and killing dozens of people.
The operations in the north have led to renewed refugee flows into Turkey, Turkish officials say, and on Thursday night Syrian forces crossed 200 meters into Lebanese territory in pursuit of fugitives, according to the Lebanese Army. Lebanese sources said a Lebanese man was wounded in gunfire.
Activists said most of Friday's killings occurred in the countryside around the city of Hama and in Jabal Al-Zawiya, a rugged region near Turkey, both scenes of military operations in the last week.
