Al Qaeda-linked jihadists struck back against rival rebels in eastern and northern Syria yesterday after a week of internecine fighting among opponents of President Bashar al-Assad in which 500 people have been killed, a monitoring group said.

With fewer than two weeks to go before what is hoped will be the first peace talks between the opposition and Assad’s government, disparate opposition groups met for the first time in the Spanish city of Cordoba.

They agreed to work together but did not agree who, if any of them, should attend the talks.

Nearly three years into a conflict that has driven a quarter of Syrians from their homes and killed some 130,000 people, the opposition to Assad is fragmenting.

In rebel-held areas, other groups have turned against the al-Qaeda-linked Islamic State of Iraq and the Levant (Isil), which aims to construct an Islamist caliphate straddling the border separating Syria and Iraq.

In a coordinated offensive, rival armed groups have seized several Isil strongholds in Aleppo, on the border with Turkey, and further east in Raqqa, the only city fully under control of Assad’s foes.

But the Syrian Observatory for Human Rights said Isil fighters pushed back the rival rebels on the eastern approaches of Raqqa yesterday. They also killed 20 fighters in the town of al-Bab, northeast of Aleppo, the UK-based group said.

Prospects for progress at the peace talks in Switzerland appear dim. Assad, buttressed by recent military gains and the worst rebel infighting since the civil war began, has ruled out demands from the weakened opposition that he stand aside.

Most rebels are opposed to the negotiations, known as Geneva 2, and the main opposition group in exile, the National Coalition, has delayed a final decision on whether to attend the talks until just days before their January 22 start date.

Members of the coalition met for the first time yesterday with members of the Damascus-based opposition tolerated by Assad.

Islamist rebel figures were also present at the meeting in Cordoba, Spain, part of an effort by Western backers to unify the opposition ahead of the Geneva talks.

The various groups agreed to set up a committee to coordinate Assad’s opponents but did not reach conclusions about whether to attend the peace talks.

Their final communique repeated the demand Assad be excluded from any transition.

Major Islamist and internal opposition groups did not attend.

In a statement, the Brotherhood, which has members in the coalition, set out conditions for attending including release of detainees, opening humanitarian corridors to besieged areas and the withdrawal from Syria of Iranian, Iraqi and Lebanese Hizbollah fighters who back Assad.

Opposition figures from another coalition group, the Syrian National Council, have already said they will shun Geneva as world powers have not done enough to force Assad out.

With time until the talks running out, Western and Arab countries that oppose Assad will meet tomorrow in Paris.

US Secretary of State John Kerry will hold talks with Russian Foreign Minister Sergei Lavrov on Monday, according to Russia’s Interfax news agency.

Moscow has emerged as Assad’s main international backer.

Badr Jamous, Secretary-General of the National Coalition, suggested that the opposition’s position on the peace talks depends on Moscow: “We don’t need Geneva 2 if Russia thinks Assad is going to remain in power.”

Syria’s conflict started with mostly peaceful protests in March 2011 against the president but turned into an armed insurgency and then civil war after Assad’s security forces cracked down forcefully on demonstrators.

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.