NATO was Tuesday sending Patriot missile defence systems to help Turkey defend its border with Syria, with a German unit due to set sail from a Baltic Sea port.
US and Dutch Patriot units are also en route to southern Turkey, where rockets from Syria have hit civilian areas, leading Turkey to return cross-border fire in recent months.
German and Dutch advance troops were set to fly to Turkey on Tuesday as the German military loaded 130 containers and 300 vehicles onto a chartered Danish ferry at Luebeck-Travemuende port.
The cargo was headed for the Turkish port of Iskenderun, where it was set to be received by some 170 troops on January 21 and trucked to the town of Kahramanmaras, 100 kilometres from the border.
Germany is deploying about 350 troops with the Patriots on a mission that NATO and Berlin stress is a purely defensive operation, meant to support alliance member, Turkey.
Relations between Ankara and Damascus have deteriorated sharply since the Syrian regime of Bashar al-Assad started cracking down on its opponents in March 2011.
The conflict has since turned into a civil war that has claimed more than 60,000 lives, according to the United Nations, devastated vast areas and created hundreds of thousands of refugees.
Al-Assad in a rare speech Sunday dismissed the rebels as Western "puppets," earning him a hailstorm of criticism. UN Secretary General Ban Ki-moon branded the speech a "disappointment."
In Syria, the Britain-based opposition Syrian Observatory for Human Rights documented Tuesday executions from both rival sides in the 22-month Syrian conflict.
"Reports coming from Syrian refugees escaping the village of Al-Mastuma, in the northern province of Idlib, said troops have stormed the village and executed around 15 men in the village," Rami Abdel-Rahman, head of the Observatory said.
Members of the Islamist group Al-Nusra Front executed three soldiers captured on Saturday in the eastern province of Deir al-Zour, the Observatory said.
A video posted by the rebels showed three men with someone calling their names out and confirming their belonging to the Syrian religious minority Alawites, to whom al-Assad belongs.
The video then showed the three dead bodies in a hole. Rebels said one of the men is alleged to have raped a young woman.
Violence on the ground continued with government troops saying that they have killed dozens of foreign insurgents near the rebel-held town of Daraya, at the outskirts of Damascus. Activists in the capital said government shelling have targeted the al-Yarmouk, Palestinian refugee camp.
News coming from Syria cannot be verified independently as journalists are still banned by the government from entering restive areas.
Meanwhile, General Adnan Silo, who was responsible for chemical weapons in the Syrian army before defecting to the opposition some six months ago, said Syrian forces used deadly Sarin nerve gas two weeks ago in the areas of al-Bayada and Deir Balba, both in the central Homs province.
"We have received confirmation that sarin gas was used in both areas and people have suffered breathing problems, palpitations and nausea," Silo told Dubai-based Al Arabiya television, speaking from Istanbul.
Silo referred to reports carried by the New York Times of satellite pictures that "showed troops appearing to be mixing chemicals at two storage sites, probably the deadly nerve gas sarin, and filling dozens of 500-pounds bombs that could be loaded on airplanes."