International mediator Kofi Annan called Monday for an immediate halt to the killing of civilians in Syria as he arrived in Turkey for talks on the crisis.

"The killing of civilians must end now. The world must give a clear message that this is unacceptable," Annan, who is mediating on behalf of the United Nations and Arab League, said in comments carried by Turkey's NTV channel.

Western nations on Monday stepped up pleas to Russia and China to end their blockage on U.N. Security Council action over the Syrian government's deadly assault on protest cities.

But Russia showed little sign of that it would change it stance, with Foreign Minister Sergei Lavrov slamming "risky recipes" which he said risked increasing conflict in the Middle East.

Israeli warplanes pounded the Gaza Strip for a fourth day Monday, killing four more Palestinians, as a teenager died in a mystery blast, raising the death toll so far to 23.

The latest strike killed a man in his 60s and his daughter in the Jabaliya refugee camp in northern Gaza, a medical spokesman said.

Israel's assassination of a top Gaza militant, which brought hundreds of rockets raining down on the Jewish state and the danger of further escalation, has left some wondering if its policy of targeted killings is still effective.

Since Friday, when an Israeli air strike killed Zuhair al-Qaisi, head of the Popular Resistance Committees, 23 Palestinians have been killed, most of them militants, prompting armed groups to fire more than 200 rockets at southern Israel, confining a million people to bomb shelters.

Syrian regime stalwart and former defense minister Mustafa Tlass has arrived in Paris with one of his sons but they are not defecting, opposition representatives told Agence France Presse on Monday.

Tlass arrived in France from Syria with his wife and his businessman son Firas, the Paris-based opponents said. His other son Manaf, an officer in the Syrian regime's military, is believed still to be in Damascus.

Saudi Arabia and Qatar are backing "armed terrorist gangs" operating in Syria and so are responsible for the bloodshed in the country, Information Minister Adnan Mahmoud told Agence France Presse on Monday.

"Some of the countries backing armed terrorist gangs, such as Saudi Arabia and Qatar, are accomplices to the terrorism targeting the Syrian people ... and bear responsibility for the bloodletting," he said.

Gunmen killed eight people in an attack on a jewelry shop on Monday, one of several attacks in and around Baghdad that left at least 13 people dead, most of them police officers, officials said.

The attack on the shop, in the Urr neighborhood of north Baghdad, left eight people dead, the interior ministry said on its website, including the two owners of the shop and four members of the security forces.

U.N.-Arab League peace envoy on Syria, Kofi Annan, held talks with top Qatari officials on Monday after a weekend trip to Damascus where he urged leaders to end the bloodshed there, the official Qatari news agency reported.

Annan, who arrived in Doha on Sunday, met with the emir Sheikh Hamad bin Khalifa al-Thani to "review the developments in Syria," according to a statement released by the QNA news agency.

Nine suspected al-Qaida militants have been killed in an artillery attack by the Yemeni army backed by U.S. drone strikes on their strongholds in the country's south, a local official told Agence France Presse Monday.

Three extremists were killed when U.S. drones fired missiles late on Sunday targeting their weapons hideouts in Jabal Khanfar, a hill overlooking the Abyan town of Jaar, which is controlled by al-Qaida militants, the official said.

Top officials from the United States, Russia, United Nations and European Union will meet Monday to discuss deadlocked efforts to end the Israel-Palestinian conflict, the U.N. said.

It will be the first top level meeting of the diplomatic Quartet in six months and comes amid a new flare-up in violence which has left at least 21 Palestinians dead in Israeli raids on the Gaza Strip since Friday.