Syrian troops shelled several rebel strongholds overnight and on Saturday, including Douma in northern Damascus and the central city of Homs, with a watchdog reporting at least 31 people killed nationwide.

Three women were among seven killed in the bombardment of the opposition bastion of Douma, the Britain-based Syrian Observatory for Human Rights said.

Syrian opposition leaders met Saturday for a second day of talks with hopes of inking the founding principles of a future Syria, now tarnished by a 16-month long bloodshed and political chaos.

Major Syrian opposition groups gathered once more in Istanbul under the umbrella of the main opposition, the Syrian National Council (SNC), recognized by most factions as the official voice, and a "legitimate representative of Syrians" by Western and Arab powers.

The U.N. Security Council expressed "serious concern" Friday over Libya's detention of four International Criminal Court officials and called on the country to work toward their release.

A Security Council statement pointedly reminded Libyan authorities that they have to cooperate with the ICC under U.N. resolutions on the conflict last year that led to the overthrow of late strongman Moammar Gadhafi.

Egyptians began voting on Saturday in the second round of a presidential election, pitting an Islamist against a former premier of the old regime amid political turmoil and with the post's powers still undefined.

Ahmed Shafiq, ousted president Hosni Mubarak's last prime minister, faces off against the Muslim Brotherhood's Mohammed Mursi in a two-day ballot in which 50 million Egyptians are eligible to vote.

Bedouins who kidnapped a Singapore tourist in Egypt's Sinai Peninsula Friday released him after several hours, a security source said.

"He was handed over to the security forces," the source said.

Chief Palestinian negotiator Saeb Erakat will meet here next week with U.S. Secretary of State Hillary Clinton in a bid to try to breathe new life into stalled peace talks, a U.S. official said Friday.

Clinton had already met with Israeli negotiator Yitzhak Molho and "she'll see Erakat next week," State Department spokeswoman Victoria Nuland said.

U.S. President Barack Obama and his Russian and Chinese counterparts will discuss differences over what to do about the conflict in Syria at a G20 summit next week, the U.S. said on Friday.

"Obviously disagreements persist with regard to Syria, but it will be a good opportunity for the presidents to meet and work it through," said State Department spokeswoman Victoria Nuland, referring to the Mexico talks.

Most Turks oppose direct intervention by their country in neighboring Syria, a Turkish opinion poll revealed Friday, as the escalating conflict threatens to become outright civil war.

Fifty-seven percent said they were against Turkey intervening in Syria, while 11.7 percent said they were for a military confrontation with the Damascus regime, according to the poll sponsored by an Istanbul-based think-tank, the Center for Economic and Foreign Policy Studies (EDAM).

Public security in Tunisia was "normal throughout the country" ahead of Friday prayers, after which several religious groups had planned protest rallies, an interior ministry spokesman said.

At the last minute Thursday, fundamentalist Islamic groups and the moderate Muslim Ennahda party in power called off the rallies they had planned to hold following Friday prayers, after the government issued a ban.

The U.N. observer force on Friday accused both sides in the Syrian conflict of hampering its peace mission and admitted its limitations in the face of escalating violence.

France, meanwhile, said that world powers could hold a summit on the Syrian crisis as the deadly anti-regime revolt entered its 16th month.