BEIRUT/LONDON: The Syrian Observatory for Human Rights said the army repelled a Daesh (ISIS) attack southeast of Aleppo Thursday, after clashes temporarily cut a supply route linking the city to other government-held areas of Syria.

Meanwhile, six rebel factions joined Ahrar al-Sham in its battle against the Al-Qaeda affiliate in Syria, the Islamist group said.

Before the Observatory’s latest report a Syrian military source denied that the Aleppo road was cut off and said there was no Daesh attack in the area. “On the contrary, the army is expanding its control in that area,” the source said.

The Observatory, an activist group based in Britain, said fighting between Syrian government forces and Daesh militants southeast of Aleppo had blocked the Khanasser-Ithriya road, the government’s only supply route into the city.

The Syrian army and allied forces thwarted the attack and the road opened up again, the Observatory said. Daesh militants did not make any new gains in the area, it said.

The road runs from Aleppo through the towns of Khanasser and Ithriya and links up with the cities of Hama and Homs further south.

It is the army’s supply route to Aleppo city, home to around 1.5 million people, which the government and its allies took full control of in December.

Elsewhere in northwestern Syria, Islamist rebel group Ahrar al-Sham said Thursday six other rebel factions had joined its ranks in order to fend off a major assault by a powerful militant group.

The hard-line Jabhat Fatah al-Sham, once allied with Al-Qaeda and formerly known as the Nusra Front, attacked Free Syrian Army groups west of Aleppo this week. It accused them of conspiring against it at peace talks in Kazakhstan. Ahrar al-Sham, which presents itself as a mainstream Sunni Islamist group, sided with the FSA groups and said Fatah al-Sham had rejected mediation attempts. It said that any attack on its members of was tantamount to a “declaration of war.”

Rebel factions Alwiyat Suqour al-Sham, Fastaqem, Jaish al-Islam’s Idlib branch, Jaish al-Mujahedeen and Al-Jabha al-Shamiya’s west Aleppo branch said in a statement they had joined Ahrar al-Sham.

The Ahrar al-Sham statement also mentioned a sixth group, the Sham Revolutionary Brigades, and said “other brigades” had joined.

Ahrar al-Sham is considered a terrorist group by Moscow and did not attend the Russian-backed Astana peace talks. But it said it would support FSA factions that took part if they secured a favorable outcome for the opposition. The Observatory said Fatah al-Sham clashed with fighters from Ahrar al-Sham and Suqour al-Sham Thursday in the northern rebel stronghold of Idlib province.

The attack by Fatah al-Sham had threatened to wipe out the FSA groups that have received backing from countries opposed to Syrian President Bashar Assad such as the Gulf Arab states, Turkey and the United States.

Internationally viewed as a terrorist group, Fatah al-Sham has been excluded from all diplomatic efforts to end the Syrian conflict, including a recent truce brokered by Russia and Turkey. Since the new year, the group has been targeted by a U.S. airstrikes.

While Fatah al-Sham has often fought in close proximity to FSA rebels against Assad, it also has a record of crushing foreign-backed FSA groups during Syria’s complex, almost 6-year-old conflict.

The Observatory has said Fatah al-Sham appears to believe that local rebels were providing coordinates for the airstrikes.

Also Thursday, Syria’s main opposition leaders turned down an invitation from Russian Foreign Minister Sergey Lavrov for talks in Moscow.

High Negotiations Committee spokesman Riyad Naasan said that HNC coordinator Riyad Hijab had “received a personal invitation” to attend Friday’s talks “but declined.”

But “no invitation has yet been sent to the High Negotiations Committee,” he added.

The HNC is the main Syrian opposition umbrella group and took part in the peace talks brokered by Syria regime allies Russia and Iran and rebel backer Turkey in Astana this week.

The Turkey-based opposition National Coalition also declined to meet with Lavrov, spokesman Ahmad Ramadan said.

He said invitations were sent to the current and past heads of the National Coalition and to the deputy of the sitting chief.

Since Russia’s entry into the war on the side of the Syrian regime in 2015 Assad’s forces have been in the ascent, scoring a string of victories that forced rebels to the talks in Astana.

Britain’s foreign minister Thursday hinted at a shift in policy on Syria, saying Assad could be allowed to run for re-election and mentioning a possible “arrangement” with regime ally Russia.

“We were wedded for a long time to the mantra that Assad must go. We haven’t at any stage been able to make that happen,” Boris Johnson told members of a parliamentary committee in the House of Lords.

Asked if one possible scenario could include allowing Assad to contest a democratic election in Syria supervised by the U.N., Johnson replied: “Yes.”

“I see downsides and I see risks in us going in, doing a complete flip-flop, supporting the Russians, Assad.

“But I must also be realistic about the way the landscape has changed and it may be that we will have to think afresh about how to handle this,” he said.

Britain has been one of the harshest critics of Russia’s Syria policy and the Assad regime, saying that his departure is a precondition for any resolution in a conflict that has killed more than 310,000 people and forced millions to flee.

Johnson’s comments were wide-ranging and sometimes contradictory as he also mentioned the “possibility of an arrangement” with Russia for “getting rid of Assad” and fighting Daesh.

But he added: “There are perils in that approach and it’s by no means clear that we would either achieve the end of the Assad regime, nor is it clear that even if we did achieve the end of the Assad regime that Syria would be in a better place.”

Russia, Iran and Turkey Tuesday agreed to bolster a fragile truce in Syria but rebels and Damascus made no progress toward a broader settlement to end the war after talks in Kazakhstan.