BEIRUT — Russia launched new strikes in Syria on Tuesday involving carrier-borne jets and long-range missiles as opposition activists on the ground reported that the first airstrikes in nearly a month struck the besieged, rebel-held parts of the northern Syrian city of Aleppo.

According to activists, between four and 10 people were killed in the strikes on Aleppo, raising concerns of a return to daily deadly bombardment in Syria's largest city.

The Russian blitz began hours after Russian President Vladimir Putin and U.S. President-elect Donald Trump discussed Syria over the phone and agreed on the need to combine efforts in the fight against what the Kremlin called their No. 1 enemy — “international terrorism and extremism.”

The Obama administration has been trying to negotiate a cease-fire in Aleppo, a city that has become the epicenter of the war between President Bashar Assad and rebels fighting to topple him, some of whom receive U.S. aid. From the militants' side, al-Qaida's Syrian affiliate is fighting alongside the rebels, but the Islamic State group has no presence in Aleppo city.

Russian Defense Minister Sergei Shoigu reported to Putin that Su-33 jets from the aircraft carrier Admiral Kuznetsov are involved in the operation, marking its combat debut.

“We launched a major operation to strike the positions of the Islamic State and Jabhat al-Nusra in the provinces of Idlib and Homs,” Shoigu said at a meeting with Putin, referring to the al-Qaida's branch in Syria by its old name. He said the airstrikes are targeting ammunition depots, training camps and armaments factories.

As part of the Russian operation, a navy frigate launched long-range Kalibr cruise missiles and the military also used Bastion missiles stationed in Syria to strike militant targets in the rebel-held northern province of Idlib and the central province of Homs.

Shoigu said that before launching the strikes, the military intelligence had thoroughly identified and selected targets, including factories producing toxic chemical agents.

“It's a well-developed, industrial-scale production,” he said, adding that the strikes will continue. He did not mention Aleppo.

Meanwhile, Syrian activists reported strikes in Aleppo, Homs and Idlib.

The Britain-based Syrian Observatory for Human Rights said missiles fired from Russian warships in the Mediterranean struck areas in Aleppo province and on the eastern edge of nearby Idlib. The Observatory's chief, Rami Abdurrahman, said the areas hit with missiles are strongholds of jihadi groups, including the al-Qaida affiliate known as Jabhat Fatah al-Sham Front.

The Observatory and other groups said airstrikes also struck at least eight neighborhoods in Aleppo city, killing at least 10 people. The Local Coordination Committees, another activist group, said the airstrikes on Aleppo killed four and wounded others.