Protesting the lack of global condemnation for atrocities in Syria, the country's main opposition coalition said Saturday it would not attend upcoming talks in Italy, Russia and the United States, DPA reported.
"Due to this shameful international position, the coalition has decided to suspend its participation in the Friends of Syria Conference of international powers due in Rome on Thursday and talks in Russia and the US," the National Coalition of Syrian Revolutionary and Opposition Forces said.
The boycott decision came a day after dozens of people were reportedly killed in a missile attack by troops loyal to Syrian President Bashar al-Assad against a residential area in the northern city of Aleppo.
In Cairo, Syrians staged a protest near the headquarters of the Arab League in which the head of the National Coalition Moaz al-Khatib urged the world's governments to make "serious efforts" to end the bloodshed in his country.
"I am participating in this sit-in to show that the decision taken by the coalition is a scream of condemnation of the world, which is watching the Syrian people being killed," al-Khatib told the rally.
The coalition also lashed out at Russia for continuing to supply weapons to al-Assad's regime.
Al-Khatib was due to visit Moscow in early March for landmark talks with Russian officials.
Russian Foreign Minister Sergei Lavrov this week called for direct talks between the Syrian opposition and al-Assad's regime.
He said that there was no hope for a military solution to Syria's nearly two-year conflict.
In Syria, at least 80 people were killed on Saturday, including 31 in the embattled city of Aleppo, said activists.
The opposition Syrian Observatory for Human Rights said government troops were using surface-to-surface missiles to drive rebels out of their strongholds in Aleppo.
Both sides have been battling for months for control of Aleppo, Syria's commercial hub.
At least 70,000 people have been killed in Syria since the uprising against al-Assad's rule started in March 2011, according to UN estimates.
Meanwhile, German Defence Minister Thomas de Maiziere and his Dutch counterpart Jeanine Hennis-Plasschaert visited the Turkish cities of Adana and Kahramanmaras near the border with Syria to inspect the Patriot batteries provided by their countries at Turkey's request.
"The Patriot system is strictly for defence, and placing them on our soil within the NATO framework was to protect our people and our soil against possible attack," said Turkish Defence Minister Ismet Yilmaz, who accompanied the Dutch and German delegations.
German Chancellor Angela Merkel was scheduled to visit the area on Sunday when she starts a two-day visit to Turkey.