Turkey's top brass held talks Wednesday about the activities of Kurdish rebels in Syria, after press reports that they were in control of several northern areas of the conflict-torn nation.

"The latest developments in Syria, the activities of the terrorist separatist group in our country and in neighboring countries were discussed at the meeting," Prime Minister Recep Tayyip Erdogan's office said.

About 300 people fled from Syria into Turkey overnight, amid guarantees by Ankara to keep the border open to refugees, the U.N.'s refugee agency said on Wednesday.

"I can confirm we not only have assurances from the Turkish authorities that borders remain open for Syrians fleeing the violence, but also we know that around 300 people crossed last night," said Sybella Wilkes, spokeswoman for the U.N.'s High Commissioner for Refugees.

More than 100 Palestinian families have returned to Gaza over the past week after fleeing spiraling violence in war-torn Syria, a Palestinian NGO said on Wednesday.

According to Hamza Abu Shanab, who heads the Palestinian Assembly for Supporting the Syrian Revolution, the families have begun crossing through the Rafah crossing from Egypt over the past week.

Russia on Wednesday lashed out at the United States for backing the armed opposition to the Syrian regime, saying Washington's failure to condemn the July 18 blast that killed top security officials meant it was justifying terror.

"This is quite an awful position, I cannot even find the words to make clear how we feel," Lavrov told reporters. "This is directly justifying terrorism. How can this be understood?"

Syrian Ambassador to the United Arab Emirates Abdul-Latif al-Dabbagh has defected, al-Jazeera TV reported Wednesday.

The Doha based television said that Dabbagh defected but it did not say where he was.

Half of the members of the United Nations observer mission in Syria have left the country, two mission members told Agence France Presse on Wednesday.

"One hundred and fifty observers left Syria on Tuesday evening and Wednesday and they will not come back," one observer told AFP.

Russia condemned on Wednesday a new round of EU sanctions against Syria over the prolonged conflict with the opposition as amounting to an air and sea "blockade" of its Soviet-era ally.

"Essentially, the measures taken by the European Union can be considered a declaration of a sea and air blockade of Syria," the Russian foreign ministry said in a statement.

Al-Qaida's Iraq front group claimed a wave of attacks that killed 113 people on Monday in Iraq's deadliest day in two and a half years, saying it marked the launch of a new campaign promised by its leader.

"As part of the new military campaign aimed at recovering territory given up by the Islamic State of Iraq (ISI), the war ministry has sent its sons and the mujahedeen on a sacred offensive during the month of Ramadan," the group said in a statement posted on jihadist website Honein.

Turkey will close its border crossings with neighboring strife-torn Syria on Wednesday until further notice, a Turkish official told Agence France Presse.

"We have taken such a measure for our citizens for security reasons," said the official. "This is an open-ended measure and the reopening depends on the developments on the ground."

The Syrian army and rebels deployed more forces in and around Aleppo on Wednesday as a "decisive" battle for control of the country's second city raged, activists and regime sources said.

"Hundreds of rebels from all over the north of Syria are arriving in Aleppo, which appears to have become the decisive battle," a journalist for a Syrian newspaper working in the city told Agence France Presse.