Terrified residents fled a new wave of air strikes on rebel-held areas of Syria's divided city of Aleppo on Saturday, as key regime backer Russia rejected calls to rein in its ally.

Aleppo was left out of a new temporary U.S.-Russian brokered truce that appeared to be holding in the regime stronghold of Latakia as well as Damascus and the nearby rebel bastion of Eastern Ghouta.

Key regime backer Russia on Friday downplayed the significance of the departure of Syria's main opposition group from U.N.-brokered peace talks in Geneva earlier this week.

"Probably no one loses but them if they leave the negotiations," Russian Foreign Minister Sergei Lavrov said on a visit to Armenia, referring to the opposition High Negotiations Committee (HNC).

Israeli Prime Minister Benjamin Netanyahu met Russian President Vladimir Putin in Moscow Thursday over fears the Kremlin's involvement in Syria and weapons deliveries to Iran could bolster the Jewish state's fiercest opponents.

"Israel has obvious and evident red lines connected to our security," Netanyahu told Putin at the start of the meeting.

Russia has kept a considerable military presence in conflict-torn Syria to bolster the regime of President Bashar Assad, NATO chief Jens Stoltenberg said Thursday.

"Despite the announced partial withdrawal we see that Russia maintains a considerable military presence in support of the Assad regime in Syria," he said at a press conference in Turkey.

NATO and Russia ran up against "profound disagreements" over Ukraine and other issues as their ambassadors met on Wednesday for the first time since 2014, alliance chief Jens Stoltenberg said.

The two sides agreed to keep communicating following the meeting of the NATO-Russia Council, which has been on ice since the alliance cut practical ties with Moscow to protest the annexation of Crimea from Ukraine in early 2014.

Ukrainian President Petro Poroshenko said on Tuesday that jailed pilot Nadiya Savchenko had agreed to end her hunger strike in a Russian jail, as Kiev tries to hammer out a prisoner swap deal with Moscow.

Poroshenko spoke by phone with Savchenko who was jailed by a Russian court last month on murder charges.

A Ukrainian court on Monday sentenced two alleged Russian soldiers to 14 years in prison for fighting in the rebel east, in a ruling that could prelude a swap for pilot Nadiya Savchenko jailed by Russia.

The verdict from a panel of three judges read out in court said sergeant Aleksander Aleksandrov and captain Yevgeny Yerofeyev were guilty of participating in "an aggressive war" against Ukraine and committing "a terrorist attack".

The powerful chief of Russia's equivalent to the FBI on Monday called for sweeping new rights restrictions, including curbing Internet freedoms and making it illegal to question Moscow's annexation of Crimea from Ukraine.

The head of Russia's Investigative Committee Alexander Bastrykin backed a radical crackdown citing the need to counteract the "destructive" influence of the United States.

A U.S. Air Force reconnaissance plane was intercepted by a Russian SU-27 jet in an "unsafe and unprofessional" manner while in international airspace over the Baltic Sea, the Pentagon said Saturday.

"The U.S. aircraft was operating in international airspace and at no time crossed into Russian territory," Laura Seal, a Pentagon spokeswoman, said of Thursday's incident.

President Vladimir Putin said Thursday that Moscow is in contact with Kiev over a possible prisoner exchange for Ukrainian pilot Nadiya Savchenko, jailed over the killing of two Russian journalists.

"We are in contact on this issue with the leadership of Ukraine," Putin told journalists after his annual televised phone-in.