The complex Syria ceasefire deal agreed by the U.S. and Russia faces numerous challenges, from the deep mistrust between rebels and regime to the web of actors drawn into the war.

Two bomb blasts outside a shopping mall in central Baghdad claimed by the Islamic State group killed at least 13 people, security and medical officials said on Saturday.

The bombings were the latest in a series of deadly attacks at Baghdad shopping centres this year that have been claimed by IS, including one that killed more than 300 people in early July.

Turkey, which has sent dozens of tanks and hundreds of troops into Syria in an unprecedented incursion, on Saturday welcomed a deal agreed by the United States and Russia for a ceasefire in its conflict-torn neighbor.

"We welcome the agreement," the foreign ministry said in a statement, saying it was essential that fighting was halted across Syria and humanitarian aid reaches those in need "from the first day" of the ceasefire on the Islamic Eid al-Adha holiday starting Monday.

A Syrian opposition umbrella group said on Saturday it welcomed a complex truce deal brokered by Moscow and Washington provided it was honored by the regime. 

"We hope this will be the beginning of the end of the civilians' ordeal," leading High Negotiations Committee member Bassma Kodmani said. 

Escalating violence in South Sudan is casting a light on Israel's murky involvement in that conflict and raising questions about Prime Minister Benjamin Netanyahu's new strategy of strengthening ties with African countries.

Netanyahu has been forging alliances across Africa in an effort he says will help blunt Palestinian diplomatic initiatives against Israel at the United Nations.

The United States and Russia reached a deal on a new Syrian ceasefire, which, if it holds, could see the first joint military effort by the two powers against jihadists.

U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov said that the truce, reached late on Friday, would come into force on Monday, the first day of the Muslim holiday of Eid al-Adha.

An air strike near Syria's battleground second city Aleppo has killed the commander of the largest rebel alliance in the biggest blow since its formation early last year, a monitor said Friday.

The strike on a meeting of leaders of the Army of Conquest alliance came hot on the heels of a major defeat for the rebels, which saw them under renewed siege inside Aleppo after an army advance this week. 

With the Islamic State group on the back foot after a string of military defeats, foreign volunteers for the jihadist group are returning home and creating a massive security challenge, experts say.

The United States and Russia will make a fresh bid to end the bloodshed in Syria Friday, as Moscow-backed regime forces make new advances against rebel fighters on the ground.

U.S. Secretary of State John Kerry flew into Geneva for crunch talks with his Russian counterpart Sergei Lavrov, with Washington warning talks could not go on forever without a breakthrough.

Iraq and Syria have been so thoroughly damaged by warfare, sectarian conflict and killing that it is unclear they "can be put back together again," CIA Director John Brennan said.

In an interview this week with the CTC Sentinel, a publication from the West Point military academy's Combating Terrorism Center, the head of the Central Intelligence Agency said the current system of governance in the two countries might change altogether.