Syrian troops and allied forces have reached the eastern city of Deir el-Zour, breaching a near three-year Islamic State group siege on government-held areas, reports said.
State TV said troops advancing from the west reached the outskirts of the contested city near the Iraqi border and broke the siege after IS defences collapsed.
Breaking the siege on Deir el-Zour, which has been divided between IS and government troops 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 had met.
The defence ministry in Moscow said a Russian warship in the M editerranean had fired cruise missiles towards IS targets in Deir el-Zour province.
A Russian frigate in the Mediterranean Sea fired the missiles early on Tuesday at IS targets near the city.
The 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 drone footage showed that the missile strikes destroyed a communications centre, command centres, ammunition depots and a workshop for armoured vehicles, and killed an unspecified number of militants.
The breakthrough came after government forces dismantled mines around a besieged government-held air base known as Brigade 137.
The DeirEzzor 24, an activist group with reporters throughout the eastern province, reported heavy clashes near the village of Jabra, close to the besieged area.
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 US-backed Syrian forces in its self-proclaimed capital of Raqqa, north-west of Deir el-Zour.
Government troops and allied militiamen, backed by Russia's air force, have for months been advancing towards 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 neighbourhoods controlled by the government and a nearby airport.
The developments came a day after the defence ministry in Moscow said two Russian troops were killed in shelling in Syria's east.
The ministry's statement quoted by Russian news agencies said the two men died when a convoy escorting Russian ceasefire monitoring staff came under mortar fire outside the city of Deir el-Zour.
The ministry said one man died at the scene and the other died later in hospital.