"We will not keep silent when, every day, in Syria, innocent babies, women and people are murdered," Mr Erdogan said.
"We are not going to keep quiet about the silent Satan of Syria, its ruthless dictator who condoned those powers occupying its own territory for decades yet massacres his own people without mercy."
Turkey and Syria are former allies but Mr Erdogan has been outspoken in his condemnation of the Assad regime since civil war erupted in March 2011.
Addressing an audience of more than 2,000 yesterday at a conference on how governments communicate with their people, Mr Erdogan criticised inaction in other world trouble spots.
"When the children are losing their lives in Palestine or Gaza, we are not turning a blind eye or going to be like those who are keeping silent," he said.
"We are not and will not be like those who kept silent in the face of hunger in Somalia, poverty in Myanmar, misery in Afghanistan and discord in Iraq," the prime minister said.
"Those who only speak with their tongues can only construct sentences with the words they know. Those who only look through their eyes, can only see as far as the horizon.
"Indeed, in our world, to say things that you have not done or not do the things which you have promised, is one of the biggest mistakes in our understanding.
"However, only saying and then doing it is not enough. We have to keep in mind another fundamental principle: a person who does not speak out against injustice is a silent Satan.
"It is our responsibility to say the just, raise our voice against injustice, correct this with the help of a hand, or a tongue or, if all these are not possible, to disassociate our hearts from this injustice."
More than 500 political figures, media personalities and representatives of government departments attended the forum to discuss and examine the development of government communication mechanisms in the region.
The former United Nations secretary general Kofi Annan and Amr Moussa, former secretary general of the Arab League, spoke of how changes across the world were to blame for limited communication between governments and their people.
Mr Moussa told the audience one of the main reasons the Mubarak regime in Egypt collapsed was its failure to communicate.
"During the early years of the 21st century, major economic changes were taking place in Egypt and the government kept quiet. This caused a lot of anger to brew in the country that finally erupted with the revolution," he said.
"We have witnessed a watershed moment in the Arab world and, while the momentum for change may be slow, it will never stop."
He said countries in the region might progress at different speeds but the direction was the same: the abolition of dictatorship and despotism.
Mr Annan said effective communication, cooperation and trust were the key factors in tackling the changes the world was facing.
"The levels of trust between the world's governments and citizens are currently so low," he said.
The world was wired together and "the hunger for knowledge insatiable" yet, until now, effective government communications do not exist in the region.
"Worryingly, the scale and complexity of these challenges, whether climate change, social conflicts, civil wars or terrorism, seem to have outgrown our political institutions or financial frameworks," he said.
"Political leaders have struggled to keep pace with the flow of problems and this has fuelled anger and frustration with the people who feel some leaders are reluctant to take difficult decisions that are necessary."
Mr Annan urged governments to take a more interactive role and engage the public by taking advantage of social media.