The Syrian army announced on Friday it liberated the long-contested eastern city of Deir el-Zour from the Islamic State group — a largely symbolic victory in the military's bigger fight to capture the last remaining Islamic State strongholds in the oil-rich province along the border with Iraq.

In a statement, the military said it was now in full control of the city, after a weeks-long campaign carried out with allied forces. It said army units were now removing booby traps and mines left behind by the extremist group in the city.

Deir el-Zour, on the west bank of the Euphrates River, had been divided into a government-held and an Islamic State-held part for nearly three years.

Syrian government forces and their pro-government allies first broke the militant group's siege of their part of the city in September in a Russian-backed offensive, and have been advancing against Islamic State positions since then.

The city is the largest in eastern Syria and the capital of the province with the same name.

The development is the latest significant defeat for Islamic State as the militant group sees its self-proclaimed "caliphate" crumble and lose almost all urban strongholds, including Mosul in Iraq and Raqqa in northern Syria. It also comes as Iraqi forces and allied Shiite militiamen are chasing Islamic State remnants inside the town of Qaim, on the Iraqi side of the border.

The Syrian army, backed by Russia and Iran, and Kurdish-led Syrian forces, backed by the United States, are now racing to take the rest of the oil-rich eastern province of Deir el-Zour, including the key town of Boukamal near the Iraqi border.

Moscow's military involvement in the Syrian war since 2015 has propped up President Bashar Assad's forces and turned the conflict in his favor, while Russian mediation earlier this year launched cease-fire talks in Astana, Kazakhstan. The talks, sponsored jointly with Iran and Turkey, have brokered local deals that have significantly reduced violence in the war-torn country.

"Army units, in cooperation with allied forces, liberated the city of Deir al-Zour completely from the Daesh terrorist organization," the military statement said, using the Arabic name for Islamic State.

Footage posted on the website of the Syrian state news agency SANA shows the last moments of the fighting between the Syrian army and Islamic State in Deir el-Zour, including shelling by Syrian tanks and plumes of smoke rising over the city's Islamic State-held and mostly destroyed neighborhoods of Jamiayat and Jabiliyeh before they were liberated.