Syrian government troops and allied forces reached the eastern city of Deir el-Zour on Tuesday, breaching a nearly 3-year Islamic State group siege on government-held areas of the contested city near the Iraqi border, Syrian state TV and a war monitoring group said.

The TV said troops advancing from the west reached the western outskirts of the city and broke the siege after IS defenses collapsed.

Breaching the siege on Deir el-Zour, which has been divided between an IS and a government-held part since 2015, marks another triumph for President Bashar Assad, whose forces have been advancing on several fronts against IS and other insurgent groups over the past year.

Rami Abdurrahman who heads the Britain-based Syrian Observatory for Human Rights also said advancing troops and those defending the city have met.

The latest developments mark a strategic and symbolic defeat for IS, which last month lost its hold over Iraq's second largest city of Mosul and is under attack by U.S.-backed Syrian forces in its self-proclaimed capital of Raqqa, northwest of Deir el-Zour.

Syrian troops and allied militiamen, backed by Russia's air force, have for months been advancing toward Deir el-Zour, the provincial capital of the oil-rich province of the same name. The breach is expected to end a nightmare siege for tens of thousands of people trapped in a handful of neighborhoods controlled by the government and a nearby airport.

Russia's Defense Ministry said Tuesday that a Russian warship in the Mediterranean fired cruise missiles toward Islamic State group targets in Deir el-Zour province.

IBTPOTY2017 Pictures of the week
8 August 2017: A huge cloud of dust and smoke billows following a reported air strike on a rebel-held area in the southern Syrian city of DaraaMohamad Abazeed/AFP

A Russian frigate in the Mediterranean Sea fired the missiles early Tuesday on IS targets near the city. The defense ministry said it targeted a fortified area around the town of el-Shola where most of the militants are believed to hail from Russia and former Soviet republics.

The ministry said its drone footage showed that the missile strikes there destroyed a communications center, command centers, ammunition depots, a repair shop for armored vehicles and killed an unspecified number of militants.

Tuesday's breakthrough came after government forces dismantling mines around a besieged government-held air base known as Brigade 137.

The DeirEzzor 24, an activist group that has reporters throughout the eastern province, reported heavy clashes near the village of Jabra that is adjacent to the besieged area.

Tuesday's firing of cruise missiles came a day after the Russian defense ministry said two Russian troops were killed in shelling in Syria's east.

The ministry's statement quoted by Russian news agencies late on Monday said the two men died when a convoy escorting Russian cease-fire monitoring staff came under mortar fire outside the city of Deir el-Zour.

The ministry said one man died on the spot and the other died later of his wounds in a hospital.