The army and allied forces have made a swift lunge through militant lines in recent days
The Syrian army linked up on Tuesday with troops that the Islamic State (IS) group had encircled for years in the eastern city of Deir Ezzor, breaking the siege, state media said.
A military media unit run by Hezbollah, a key Damascus ally, said the advancing forces reached an army garrison at the edge of the city.
Syrian President Bashar al-Assad called army commanders who had been besieged, to congratulate them.
"Today you stood side-by-side with your comrades who came to your rescue and fought the hardest battles to break the siege on the city," Assad said in the call with the commanders of troops who had been besieged in a base in Deir Ezzor.
The army and allied forces have made a swift lunge through militant lines in recent days to relieve an enclave in the Euphrates city, where IS has besieged the garrison and some 93,000 civilians since 2014.
"The Syrian Arab Army has advanced on the Brigade 137 base front on the western side of Deir Ezzor city and broken the siege imposed by the Daesh organisation," state news agency SANA said, using the Arabic acronym for IS.
IS had since 2014 besieged the government-held enclave, where some 93,000 civilians live and an army garrison is stationed.
Deir Ezzor is located southeast of IS's former stronghold Raqqa, most of which has been captured in a separate offensive by US-backed Syrian militias.
Islamic State group militants are believed to have fled to areas around Deir Ezzor as the group loses areas of Raqqa.
Telegram from Putin
Russian President Vladimir Putin sent a telegram to Assad, hailing the breaking of the siege, the Kremlin said on Tuesday.
Kremlin spokesman Dmitry Peskov told a conference call with reporters that Putin had hailed the breakthrough as "a strategic victory" over Islamic State militants.
Street-to-street fighting was now underway in Deir Ezzor, Peskov said.
Russian air strikes that struck Islamic State targets in the city on Tuesday helped Syrian government troops in the area swiftly advance, he said, citing a Russian Defence Ministry report to Putin.