Saudi Arabia has backed the arming of Syria's opposition guerrilla army in remarks that could signal an intervention by the Sunni Muslim superpower in the Assad regime's crackdown on an anti-government uprising.

The Saudi foreign minister, Prince Saud al-Faisal, described the arming of the Free Syrian Army as an "excellent idea" at an inaugural meeting inTunisia of an anti-Assad group the Friends of Syria, convened to find a solution to the crisis ravaging the country.

But the Saudi delegation later walked out of the summit citing "inactivity" among the member states gathered.

Qatar's foreign minister, Sheikh Hamad bin Jassim al-Thani, called for the creation of an Arab force to "open humanitarian corridors to provide security to the Syrian people".

In the Syrian city of Homs, the International Committee of the Red Cross (ICRC) said it had begun to evacuate women and children from the Baba Amr district, where western journalists including the injured Le Figaro reporter Edith Bouvier and the Sunday Times photographer Paul Conroy had become stranded.

The first day of the three-day summit in Tunis offered little to stem the fast deteriorating situation in Syria, although key stakeholders, including key Syrian ally Russia did moderate positions that had calcified a political standoff over the past six months as the violence worsened.

In Baba Amr, where 20,000 residents remain under military siege, neither the west nor the opposition Syrian National Council are seen as saviours. "Nothing has changed it is the same situation, the same siege," one resident told the Guardian. "They keep killing and nobody cares about our lives. We feel a lot of anger.

"Is there any real action from the world? We don't want statements. He [President Bashar al-Assad] will never stop. He will keep killing. We want them to protect our families, our children, our women. To provide food, to provide medicine. To remove this dictatorship from our head.

"Any kind of protection for civilians would be welcome. Military [intervention] would be welcome. We want action to stop the bloodshed. We want them to remove Bashar al-Assad."

Russia on Friday added its voice to calls for a ceasefire to allow aid to reach areas in desperate need, such as Homs. Hopes for a ceasefire had been a centrepiece of the summit, which is being attended by almost 80 countries, many of whom are looking for ways to embolden Syria's opposition movement.

Britain took the first step in that process,has formally recognising the SNC as legitimate representatives of the Syrian people in a move it hopes will propel the disjointed opposition and generate a global shift away from Assad's regime.

The foreign secretary William Hague's announcement marks the first time a western state has given full backing to the nascent opposition, which had failed to lock in patrons despite a brazen and ferocious year-long regime assault on dissent.

Hague chose the summit's opening minutes to sever ties with Damascus, which has ignored repeated calls to withdraw its forces to barracks and enter into power-sharing talks.

He called on leaders of the 80 states represented in Tunis to "tighten the diplomatic and economic stranglehold" on the Syrian government, whose leaders have been already been hit with a series of increasingly harsh sanctions.

"We, in common with other nations, will now treat them and recognise them as a legitimate representative of the Syrian people," Hague said.

At the same time, the US, France and other western countries are pushing Assad to agree to a ceasefire, particularly in Homs, which was on Friday again pounded by rockets and shells for a 21st consecutive day.

In Gaza , leaders of the Palestinian Islamist movement Hamas publicly endorsed the opposition movement in Syria, depriving Assad of one of his few remaining Sunni Muslim supporters in the Arab world, deepening his international isolation.

The SNC has signalled it will drop its objection to arm the opposition Free Syria Army, which is battling loyalist military. The SNC has suggested it would no longer oppose foreign military trainers, advisers, or even weapons, if the regime failed to agree to the terms of an Arab League initiative to end the violence.

"If the regime fails to accept the terms of the political initiative outlined by the Arab League and end violence against citizens, the Friends of Syria should not constrain individual countries from aiding the Syrian opposition by means of military advisers, training and provision of arms to defend themselves," the SNC said.

The key plank of the Arab League plan was a call for Assad to stand down, something which he, along with his allies, Russia, China and Iran, have rejected.

Instead, he is pushing ahead with a referendum on a new constitution, scheduled for Sunday[tomorrow], which aims to reorientate the totalitarian state towards a more pluralistic political system.

Hague called Assad's government "a criminal regime", suggesting he had little faith in the reform measures mooted by Damascus. Despite mounting pleas from inside rebel-held areas to send weapons in a Libya-style intervention, he said Britain would continue to abide by the terms of a EU arms embargo on Syria. "There may well be people who say that," he said of the renewed pleas for weapons. "And it reflects the intense frustration that we all feel."

The US this week edged away from its earlier insistence that it too would refrain from sending weapons to rebels, a stance influenced by its intelligence assessments from inside Syria that the Free Syria Army remains a poorly defined and disciplined force that operates more as a series of franchises than a resistance military.

The Friends of Syria conference marks the best opportunity yet for the political opposition to shake off the same misgivings and win the confidence of the west, which has waited a year before choosing to embrace it. The SNC represents only around 70% of Syria's opposition movement and had so far struggled to adopt unified stances on many key issues.