Former UN chief Kofi Annan held crux talks in Damascus on Saturday with the hopes of the world pinned on his bid to prevent a nearly year-old uprising spiralling into all-out civil war.

State media reported the start of talks between President Bashar al-Assad and Annan, on his first visit since being named international envoy on the conflict.

It came as a human rights group reported fierce shelling of Idlib in northwest Syria and a day after another 70 civilians were killed in the regime's crackdown on dissent.

Human rights watchdogs say the conflict has cost more than 8,500 lives since last March.

Emissary of the United Nations and the Arab League, Annan has the support of Damascus allies Beijing and Moscow and his mission has been welcomed by the both the Syrian government and opposition.

But Russia said its Foreign Minister Sergei Lavrov made clear to Annan at a meeting earlier in Cairo that Moscow was opposed to ‘crude interference’ in Syria's affairs.

"A particular emphasis was placed on the inadmissibility of trampling on international legal norms, including through crude interference in Syria's internal affairs," the foreign ministry said.

‘Demand immediate end to violence’

Current UN chief Ban Ki-moon said that Annan would demand an immediate end to the violence and aid agency access to besieged protest cities to evacuate casualties and provide desperately needed relief supplies to civilians trapped by the fighting.

"I very strongly urged Kofi Annan to ensure there must be an immediate ceasefire," Ban said. "I also asked him to urge Assad to facilitate humanitarian assistance and access."

Ban said that Annan would seek to encourage dialogue between Assad's government and the opposition but that he would not meet opposition figures inside Syria and would not travel outside Damascus on his two-day visit.

His predecessor would meet Assad, other government officials, "civil society" representatives and aid workers in the Syrian capital, Ban told reporters at UN headquarters.

"He will be engaging with opposition leaders outside of Syria," Ban added. "There should be an inclusive political solution."

Annan to visit neighbouring countries too

When he leaves Damascus on Sunday, Annan will travel on to neighbouring countries to press his mission to end the bloodshed, the UN chief said.

Diplomatic sources said his first port of call would be Turkey, which has taken a very tough line against Assad's regime over its deadly crackdown.

As the Annan mission was starting, Syrian troops heavily shelled the northwestern protest city of Idlib, close to the border wityh Turkey, in an apparent prelude to a ground assault, a watchdog said.

"It's the heaviest bombardment since troop reinforcements were sent to Idlib earlier this week," the head of the Britain-based Syrian Observatory for Human Rights, Rami Abdel Rahman said.

Annan's visit comes a day after UN humanitarian chief Valerie Amos left Damascus following a hard-won but troubled mission to secure relief access to protest centres such as Syria's third-largest city Homs.

After a brief visit to Homs on Thursday, Amos said much of the city had been ‘devastated’ by the intense bombardment of rebel neighbourhoods by regime forces in recent months.

Twenty-eight of the 70 people killed in Syria on Friday lost their lives in Homs, the Syrian Observatory said.

Speaking in Ankara on Friday, Amos said a ‘joint preliminary humanitarian assessment mission’ had been agreed, to provide assistance to people urgently in need of it.

No UN aid agencies are currently allowed into Syria and information is scarce on the details of the civilians' needs. But a UN spokeswoman in Geneva said 1.5 million people might be in need of food aid.

Following Amos's visit, China on Friday offered $2 million in aid to improve the humanitarian conditions in different parts of Syria.

Beijing and Moscow have drawn Western anger by blocking Arab- and Western-led efforts at the UN Security Council to pile pressure on Assad's regime.

Both used their veto powers as permanent members to block resolutions in October and again last month.

US Secretary of State Hillary Clinton said she would seek Moscow's support when she meets her Russian counterpart Lavrov on the sidelines of a Security Council meeting on the Arab Spring in New York on Monday.

Russia said it regarded the latest US draft as ‘unbalanced’ because it did not contain a call for a simultaneous halt to violence by Syrian government forces and the rebels.

The Russian foreign minister was to join his Arab counterparts in Cairo later on Saturday for talks on the Syrian crisis.