U.S. officials say they are working with nations in the Middle East to secure Syria's chemical and biological weapons sites.

"We're not talking about ground troops, but it depends on what ... happens in a transition," Defense Secretary Leon Panetta said Thursday.

Asked whether he had ruled out putting U.S. troops in Syria to secure such weapons, Panetta said: "You always have to keep the possibility that, if there is a peaceful transition and international organizations get involved, that they might ask for assistance in that situation. But in a hostile situation, we're not planning to ask for that."

Russian navy holding exercises off Syria's coast

Ships of the Russian Black Sea Fleet are heading to the eastern Mediterranean for exercises, the Russian Defense Ministry said.

A tactical group of Black Sea Fleet warships, headed by the cruiser Moskva, will undertake exercises in the eastern sector of the Mediterranean Sea. The tanker Ivan Bubnov has fueled the ships, and emergency drills have been carried out for the upcoming exercises. The tanker filled up on fuel and water Thursday at the Cyprus port of Larnaka.

A Baltic Fleet group consisting of the patrol vessel Yaroslav Mudry and tanker Lena will head for the eastern Mediterranean, where the two ships will practice stores transfers at sea. The patrol vessel will carry out anti-submarine warfare drills.

Russia has a maintenance naval base at Tartus on the coast.

No let-up in refugee flight

The United Nations said Friday that more than 612,000 people have been registered as Syrian refugees or are "being assisted as such."

There were 194,769 in Lebanon, 176,569 in Jordan, 153,163 in Turkey, 69,282 in Iraq, 13,292 in Egypt and 5,059 elsewhere in North Africa, the U.N. refugee agency said.

"Even with the winter preparation work that has been done in recent months, many refugees in both camp and noncamp situations are facing particularly cold and damp conditions. At the same time, there has been no let-up in the numbers of people fleeing Syria into neighboring countries," the U.N. High Commissioner for Refugees said.

Mia Farrow to meet refugees

Actress and UNICEF goodwill ambassador Mia Farrow will visit Lebanon next week to meet with Syrian refugees, the organization said Friday.

"As part of her mission she will appeal for additional international assistance as the needs and numbers of those fleeing Syria continue to rise," UNICEF said.

Farrow will travel to two locations near the Syrian border to meet with refugees and host families. "Ms. Farrow will also help distribute winter clothing while there as many of the refugees fled Syria with very few belongings."

Brutal winter weather is making dire conditions even more so in parts of the Middle East, especially for thousands of Syrian refugees enduring frigid temperatures in tents.

More deaths

The Syrian crisis started in March 2011, when peaceful protesters demanding democracy and reforms were met by a fierce government crackdown, which spiraled into an armed opposition movement and a civil war.

At least 106 people were killed Friday, the opposition Local Coordination Committees of Syria said. Among them were 40 people killed in shelling by artillery and jet fighters in Hasaka province, in the northeastern part of the country.