Countries have more than doubled the number of Syrian refugees they are willing to resettle to over 100,000, the head of the U.N. refugee agency said Tuesday.

"Today, 28 countries expressed their solidarity with the Syrian refugees but also with the five neighboring countries which are hosting them... offering what we estimate will be more than 100,000 opportunities for resettlement and humanitarian admission," Antonio Guterres told reporters after a high-level pledging conference in Geneva.

The U.N. envoy to Syria held "constructive" talks with rebel groups on a plan to suspend fighting in the country's second city of Aleppo, his spokeswoman told Agence France-Presse on Tuesday.

A day after Staffan de Mistura's meetings in Gaziantep, Turkey, one rebel chief said he was awaiting a "written proposal from the U.N., with all the details, before announcing a decision".

A top Emirati court on Tuesday sentenced 11 Islamists to up to life imprisonment for links to al-Qaida-affiliated militants as well as rebels in Syria, official media reported.

The Federal Supreme Court convicted them of bomb-making and of joining and financing al-Qaida franchise al-Nusra Front and Islamist rebel group Ahrar al-Sham, both in Syria.

Iranian President Hassan Rouhani called Tuesday for a regional response to the threat posed by the Islamic State group in Iraq and Syria rather than the deployment of troops from further afield.

"If countries in the region agree, they could eliminate anti-Islamic groups like Daesh and liberate thousands of men, women and children who have lost their homes," Rouhani told an anti-extremism conference in Tehran, using the Arabic acronym for IS. 

More than 50 Syrian and international rights organisations made a joint appeal Tuesday for the release of four Syrian activists abducted near Damascus a year ago.

Razan Zeitouneh, Wael Hamada, Samira Khalil and Nazem al-Hamadi were detained in the rebel-held area of Douma on December 9, 2013.

Al-Nusra Front reportedly captured three Hizbullah fighters in the border region of Qalamun in Syria, Saudi newspaper Okaz reported on Tuesday.

The daily identified the three Hizbullah members as Hassan Mansour, Ali al-Husseini and Mohammed Abbas.

The Lebanese Army carried out precautionary military operations against posts controlled by gunmen on the outskirts of the northeastern border town of Arsal and the Lebanese al-Qalamoun region, the state-run National News Agency reported on Tuesday.

According to NNA, the military operation was carried out in the towns of Mar Tayba, Wadi Mira, al-Rahwa, Wadi al-Khayl and Wadi Hmeid.

Australia on Tuesday accused Islamic militants of using foreign fighters as "cannon fodder" and "propaganda tools" as it revealed 20 nationals have now been killed in Syria and Iraq.

More than 70 Australians are currently fighting in the two nations, the government has said, with several more deaths reported as coalition fighter planes pound Islamic State group positions.

Canadian Muslims denounced a convert's call for more lone-wolf attacks in the country Monday, just weeks after two soldiers were recently killed in the first jihadist attacks on Canadian soil.

The National Council of Canadian Muslims condemned a video message from a Canadian jihadist fighter from the Islamic State group as "abhorrent and un-Islamic."

U.N. peace envoy Staffan de Mistura met on Monday with Syrian opposition members to discuss his plan to "freeze" fighting in the country's war-ravaged second city Aleppo, his spokeswoman said.

"The talks started today at 11:00 am (0900 GMT) and lasted for eight hours with representatives from the main armed and non-armed groups," Juliette Touma told Agence France-Presse.