The United States warned Syria Monday not to even consider using chemical weapons after Damascus raised the possibility of employing its stockpile of unconventional arms in the case of an outside attack, as the EU branded the Syrian remarks as "monstrous" and "unacceptable."

"They should not think one iota about using chemical weapons," Pentagon press secretary George Little told reporters.

Russian President Vladimir Putin warned on Monday of a protracted civil war in Syria should President Bashar Assad be "unconstitutionally" removed from power by rebel fighters.

"We are afraid that if the country's current leadership is removed from power unconstitutionally, then the opposition and today's leadership may simply change places," Russian news agencies quoted Putin as saying.

Syrian regime forces on Monday reclaimed most of Damascus after a week of heavy fighting with rebels, who are using guerrilla tactics to keep a foothold in the capital, activists and regime sources said.

"Unfortunately, regime forces have taken control of almost all the capital. There are still skirmishes in the southern district of Qadam and Daraya," a suburb to the south, an activist who named himself as Omar told Agence France Presse via Skype.

Iraq on Monday rejected an Arab League call for embattled Syrian President Bashar Assad to swiftly give up power, describing it as interfering in Damascus's sovereignty.

"This call is not appropriate at this time because it is interfering in the sovereignty of another country," Deputy Foreign Minister Labid Abbawi told Agence France Presse. "There are other means to secure a peaceful transition of authority."

Turkey recalled its envoy in Aleppo on Monday as rebel fighters clashed with loyalist troops in what is Syria's second-largest city, a Turkish diplomat said.

Turkey's consul for the northern city of Aleppo, Adnan Kececi, had returned to Turkey to discuss the situation in Syria, the source said.

Prime Minister Nouri al-Maliki on Monday instructed Iraq's security forces and Red Crescent to allow in Syrian refugees and provide them with support, reversing an earlier decision.

"The prime minister directed Iraqi forces and police and the Iraqi Red Crescent to receive Syrian refugees and help them and provide them with services," state broadcaster Iraqiya television said.

Cairo has eased the visa requirements for Gazans under 40 who want to travel to Egypt through the Rafah border crossing, Palestinian officials said on Monday.

"We were officially informed by the Egyptian side about a decision to allow any Palestinian under the age of 40 to travel through Rafah with his family without a visa, starting today," said Maher Abu Sabha, director of borders within Gaza's Hamas-run government.

A wave of attacks across Iraq on Monday killed 107 people in the country's deadliest day in more than two years after al-Qaida warned it would mount new attacks and sought to retake territory.

Officials said at least 214 people were wounded in 27 different attacks launched in 18 cities, shattering a relative calm which had held in the lead-up to the start on Saturday of the holy Muslim fasting month of Ramadan.

Egypt on Monday began to release detainees held by the military following a decree last week by President Mohammed Morsi, security officials told Agence France Presse.

"Prison authorities have begun releasing the detainees," an official told AFP.

At least 23 people were "summarily executed" by regime forces in two Damascus neighborhoods on Sunday, the head of the Syrian Observatory for Human Rights watchdog told Agence France Presse on Monday.

"Sixteen people, most of them younger than 30, were summarily executed by shooting on Sunday in Mazzeh," Observatory chief Rami Abdel Rahman said, referring to an upscale district in western Damascus.