Warplanes pummeled cities across Syria on Wednesday as cluster bombs rained down over Idlib province, the opposition Local Coordination Committees of Syria said.
Thirty-nine of the 144 deaths tallied Wednesday were said to have occurred in Aleppo, where the LCC said artillery shells targeted the neighborhood of Eastern Ansari.
Russia's Foreign Ministry called for an investigation, according to Russia's state news agency Itar-Tass. "We urge all parties to contribute to ceasing armed violence in Syria as soon as possible," spokesman Alexander Lukashevich said Wednesday.
Cluster bombs explode in the air, sending dozens or hundreds of smaller bombs over an area the size of a football field, according to Human Rights Watch.
More than 70 countries have signed a treaty banning the use of cluster bombs, but neither Syria nor the United States is among them. The Syrian government has denied using cluster bombs the current conflict.
State-run media, meanwhile, said government forces killed scores of 'terrorists' outside Damascus. The government routinely uses the term to describe opposition fighters, though members of Jabhat al-Nusra -- which the United States calls a terrorist group -- have reportedly joined the rebels in fighting.
In neighboring Turkey, a U.S. ship carrying Patriot air defense systems landed Wednesday at Iskenderun Port, according to the semi-official Anadolu Agency.
The spokesman for the Turkish general staff, Major Cengiz Alabacak, said that the systems would be deployed in the southeastern province of Gaziantep and would be operational by the middle of February.
NATO foreign ministers decided in December to deploy the batteries after Syria launched Scud missiles near the Turkish border. In October, errant Syrian artillery shells hit the Turkish border town of Akcakale.
The first of six Patriot missile batteries intended to protect Turkey from Syrian threats is operational along the countries' shared border, NATO said Saturday.
Turkish Foreign Minister Ahmet Davutoglu said this month that the missile batteries will stay only as long as there is a threat.
The Syrian crisis started nearly two years ago, when President Bashar al-Assad's forces cracked down on civilians peacefully protesting government policies.
The violence led to an armed uprising and escalated into a civil war, with al-Assad trying to defend four decades of family rule against rebels demanding his ouster.
But with neither side showing any indication of backing down, it's unclear how many more thousands of civilians may die.