Syrian President Bashar al-Assad on Tuesday congratulated government troops who broke a years-long Islamic State group siege on the government enclave of Deir Ezzor city, his office said.

"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 a call with the commanders of troops who had been besieged in a base in Deir Ezzor.

Syrian forces and allied fighters arrived on Tuesday at the Brigade 137 base on the western edge of Deir Ezzor, effectively ending a siege of more than two years on part of the city.