With Russian warships off the coast of Norway heading to the Mediterranean, Russia has promised to pause fighting in Syria's rebel-held east Aleppo through Saturday, the U.N.'s humanitarian office (OCHA) told AFP, after Damascus made a similar pledge.

"Russia has told the U.N. that they will implement a daily pause of 11 hours per day for three days, counting from today Thursday," OCHA spokesman Jens Laerke said in an email Thursday, as the truce in the devastated city barely held through day one.

The 11-hour truce, which was broadly holding in besieged east Aleppo, was declared by Russia. Bashar Assad's forces, which are backed by Moscow, said late Wednesday that it would also extend the truce until Saturday, but spoke only of an eight-hour halt to the fighting.

U.N. Syria envoy Staffan de Mistura said he welcomed the daily pauses to enable medical evacuations. However, the ceasefire package also required opposition fighters from the Jabhat Fateh al-Sham group to agree to leave the city.

The United Nations says it hopes to carry out the first medical evacuations from eastern Aleppo on Friday after getting clearance from all warring parties in the devastated Syrian city. "We believe we now have all of the green lights that we need both from the Russians and the [Assad regime] and from the opposition groups," to begin evacuations on Friday, Egeland said following a humanitarian taskforce meeting.

As the Russian aircraft carrier Admiral Kuznetsov sailed through the North Sea and the English Channel on Thursday, a major Russian naval deployment in the Mediterranean would be likely to reinforce a final assault on the besieged Syrian city of Aleppo in two weeks, a senior NATO diplomat said on Wednesday. "This is not a friendly port call. In two weeks, we will see a crescendo of air attacks on Aleppo as part of Russia's strategy to declare victory there," the diplomat said.

The fleet passed by the Norwegian city of Bergen on Wednesday, the diplomat said, while Russian media has said it will move through the English Channel, past Gibraltar and into the Mediterranean Sea to the Syrian coast. A Norwegian newspaper quoted the head of the Norwegian military intelligence service saying the ships involved "will probably play a role in the deciding battle for Aleppo."

Britain sent warships to monitor the Admiral Kuznetsov. Defense Secretary Michael Fallon said Thursday that the military will watch the vessels "every step of the way." The aircraft carrier Admiral Kuznetsov and its task group are heading south from the Norwegian Sea toward the North Sea. The Type 45 destroyer HMS Duncan sailed from Portsmouth to monitor the group.

The fleet off Norway includes Russia's only aircraft carrier, the Admiral Kuznetsov, which is carrying jet fighters, and the Soviet-era nuclear-powered battle cruiser Pyotr Velikiy, or Peter the Great. Other Russian vessels in the group include the anti-submarine warships of the Severomorsk and Vice-Admiral Kulakov and support ships, Russian media has reported.

Since July 17, opposition-held districts have been under near-continuous siege by Assad's forces, after Assad cut off the last supply route from other opposition-held territory. A ceasefire that went into effect from Sept. 12 to 19 raised hopes of relief deliveries but they never materialized. On Sept. 22, the army launched a new offensive and devastating Russia backed air strikes pounded opposition areas, only halting on Tuesday. Around 400 people have been killed and more than 2,000 wounded since the assault began, according to the United Nations. Much of the once-flourishing city has been reduced to a wasteland by the air and artillery bombardment. Since December 2013, the Assad forces have dropped hundreds of barrel bombs, crude unguided explosive devices that cause indiscriminate damage, according to the Syrian Observatory for Human Rights.

Aleppo is one of the world's oldest continuously inhabited cities dating back to at least 4,000 BC. Listed as a UNESCO World Heritage site in 1986, Aleppo's citadel is a jewel of mediaeval Islamic architecture. It was damaged by a blast in July 2015. Two years earlier, fighting destroyed the 11th century minaret of the city's famed Ummayad mosque. There has also been extensive damage to the city's ancient covered market.

Syria's one-time economic hub, Aleppo and the surrounding countryside, have suffered some of the heaviest fighting of the five-year civil war that has now cost more than 300,000 lives.