BEIRUT - Lebanon's Hezbollah and Syria's army made big advances against insurgents in mountains north of Damascus on Wednesday, Hezbollah and Syrian state media said, shoring up President Bashar al-Assad's grip on the border zone.
The gains in the crucial Qalamoun region close to Lebanon against groups including the al Qaeda-linked Nusra Front follow significant defeats for Assad elsewhere, notably in Syria's northwest near the Turkish border.
Hezbollah, an Iranian-backed Shi'ite group with a powerful militia, has been a vital ally for Assad in the four-year-long conflict that has become a focal point for the struggle between Tehran and Sunni Saudi Arabia, which has backed the insurgency.
Hezbollah fighters and the army seized Talat Moussa, the highest peak in the area targeted in the offensive. Sources briefed on the situation said that move had effectively secured control of the entire area some 50 km (30 miles) from Damascus.
"Now only the final stage of the operation is left," one of the sources said.
Syrian state TV credited the advance to the army and "the Lebanese resistance", an unusual public acknowledgement of Hezbollah's role in the battle for an area used by the insurgents to ferry supplies between Syria and Lebanon.
It also said that the army was pursuing the remnants of the insurgents in the town of Fleita.
Hezbollah has unleashed heavy firepower in the offensive, including concentrated rocket bombardments. The Syrian Observatory for Human Rights, a British-based group that tracks the conflict, says this had forced many insurgents to withdraw.
The offensive had been expected for some time but was awaiting the end of winter and aimed to crush one of the risks facing Assad, who has lost much of the north and east in the war estimated by the United Nations to have killed 220,000 people.
The Observatory put the death toll in the fighting at dozens on both sides. A source briefed on the situation said Hezbollah had lost four fighters.
ISLAMIC STATE CLASHES
Since March, forces backing Assad have relinquished wide areas of Idlib province in the northwest at the border with Turkey, another country that supports the insurgency. The president also lost the Nasib crossing with Jordan to rebels.
Islamic State, the single most powerful insurgent group in Syria, has also been launching attacks on both government-held and rebel-controlled areas in central Syria, as it steps up efforts to expand beyond its strongholds.
The Observatory said the militants killed about 70 government troops in an attack on Syrian army-held areas in Homs province overnight. At least 40 Islamic State fighters were also killed in and around the town of al-Sukhna, some 300 km northeast of Damascus.
Later, Islamic State said in a statement it had seized al-Sukhna in a move that gives it control over a strategic highway that links the province of Homs with north eastern Deir al-Zor province.
The militants also said they downed a Syrian MiG jet plane near the city of Tadmr in the eastern Homs area. The army did not comment but an army source earlier said Syrian troops repelled the militants' attack in places and were still fighting in others.
An army statement said scores of "terrorists" were killed in raids in the eastern Homs countryside area without confirming the fall of the town.
General Martin Dempsey, the top US military officer, said last week he believed Assad's "momentum has been slowed" and that, if he were in Assad's position, he "would find the opportunity to look to the negotiating table".
But expectations are low for a new effort towards peace diplomacy launched by the UN Syria envoy, Staffan de Mistura.
Assad has received massive support from Russia and Iran. Alaeddin Boroujerdi, head of Iran's national security and foreign policy committee, met Assad on Wednesday and said Iran would maintain that support, Syrian state media reported.
"(Iran) will not spare any effort to help the Syrians and to strengthen their steadfastness until the achievement of victory over the terrorists," the state news agency SANA quoted him as saying in the meeting.