By Ellen Francis
BEIRUT (Reuters) - Lebanese soldiers in Islamic State captivity since 2014 are almost certainly dead, a senior security official said on Sunday, just hours after the army announced a ceasefire to hold talks over their fate.
The ceasefire halted the fighting in an Islamic State enclave at the Syria-Lebanon border, where the militants have been battling the Lebanese army on one front and Hezbollah with Syrian troops on the other.
Islamic State has held nine Lebanese soldiers captive since 2014, when it briefly overran the border town of Arsal with other militants - one of the worst spillovers of the Syrian conflict. The fate of the troops had been unknown since then.
Lebanon's army announced that its ceasefire near the northeast town of Ras Baalbeck took effect at 7 a.m (0400 GMT). Hezbollah and the Syrian army also declared a ceasefire in their attack against Islamic State in Syria's western Qalamoun region, Hezbollah's al-Manar TV said.
The ceasefire continued to hold on both sides of the border throughout the day, as sources said plans for an evacuation of the remaining militants were under discussion.
The fighting began a week ago when the Lebanese army, and Hezbollah together with Syrian government forces, launched separate but simultaneous assaults.
Both offensives have advanced towards the Syria-Lebanon frontier from opposite sides, hemming the militants into a small zone straddling the border. Lebanon's army and Hezbollah have each said the battle was nearing victory.
The Islamic State pocket marks the last militant foothold in the arid hills along the Syrian-Lebanese frontier.
Defeating Islamic State there would end years of insurgents from Syria's six-year war holding territory in the mountainous border region, and allow the two countries to consolidate control of the frontier.
The head of Lebanon's internal security agency said the army and security forces had retrieved remains thought to belong to six of the soldiers and were conducting digs on Lebanese land for two others. DNA tests were needed to confirm the identities.
"We believe, almost certainly, that these are the remains of the soldiers," said the general, Abbas Ibrahim, who mediated talks between the army and the militants. The whereabouts of the ninth soldier remain unknown.
The soldiers' families had gathered in central Beirut on Sunday and said they would hold out hope until the last minute.
Ibrahim arrived in the afternoon to give them the news.
"I know this is a difficult moment ... Liberating the land often calls for offering our souls to this country," he said as some relatives of the captives wept.
Authorities found some information about the soldiers in 2015 but had not revealed it because they could not confirm the deaths, he added.
"Those who surrendered from Daesh led us to the soldiers. The rest will be sent into Syria," Ibrahim said. "We do not bargain. We are in the position of the victor and are imposing conditions."
A military source had said earlier that Islamic State fighters had "succumbed ... and asked for the negotiations".
Hezbollah has played a major role in fighting Sunni militants along the border during Syria's war, and has sent thousands of forces to support Syrian President Bashar al-Assad.
Earlier this month, Nusra Front militants and a Syrian rebel group withdrew from Lebanon's northeastern border region. They departed for insurgent territory in Syria after Hezbollah routed them in offensives with the Syrian army.
Shi'ite Hezbollah has had a strong presence in the western Qalamoun region since 2015 after defeating Syrian rebels who controlled towns there. Some insurgents, as well as many refugees fleeing the violence, took shelter on Lebanon's side of the border strip.
In a speech last week, Hezbollah leader Sayyed Hassan Nasrallah said the Iran-backed group had begun talks with Islamic State on a truce.
Lebanon's army has said it is not coordinating its attack with the Syrian army or Hezbollah, which Washington classifies as a terrorist group.
Any joint operation between the Lebanese army and either the Syrian army or Hezbollah would be politically sensitive in Lebanon and could jeopardize the sizeable U.S. military aid the country receives.
Hezbollah and its allies have been pressing the Lebanese state to normalize relations with Damascus, testing Lebanon's official policy of neutrality towards the conflict next door.
Calls for closer ties come as Assad's government has put rebels on the back foot, shoring up its rule over the main cities in western Syria with the help of Russian air power.
A Western diplomat praised the Lebanese army's performance in the border battle in "a risky and complex operation" and said it would have been "simply unimaginable" a decade ago.
"We see no evidence of substantive cooperation (between the army and Hezbollah)," the diplomat added.
A source familiar with the talks said Hezbollah and the Lebanese army had been communicating over the ceasefires and ongoing negotiations.
Hezbollah, with the Syrian army, has handled the talks over evacuating the militants, the source.
The Islamic State fighters had asked Hezbollah and the Syrian army to let them withdraw to Syria's eastern province of Deir al-Zor.
Several hundred militants are still holed up in the enclave. As the deal continues, Ibrahim said they would go likely there.
Damascus has approved an Islamic State-Hezbollah deal that allows for transferring the militants into eastern Syria, its state media said on Sunday.
With Islamic State losing vast territories in Iraq and Syria, many of its forces have retreated to Deir al-Zor province, which remains almost entirely under its control.
(Additional reporting by Laila Bassam and Tom Perry; Editing by Alison Williams)