Patrick Cockburn: I fear this terrible massacre will be the beginning of a long civil war in Syria

Parts of Syria are convulsed by civil war, while in other areas life continues almost as normal. At the same moment as more than 30 children had their throats cut and dozens of civilians were killed by shelling in Houla in central Syria on Friday, people in Damascus were picnicking on the slopes of Mount Qassioun, overlooking the capital.

Fighting can be intense, but it is also sporadic, even in highly contested areas. Over the past week, insurgents, many of them defectors from the army, have been fighting to capture Rastan, a strategically placed town on the road running north from Homs. During the same period, militants in the small city of Douma, an opposition stronghold on the outskirts of Damascus, were involved in UN mediation over access to hospitals, the release of detainees and the restoration of services. Soldiers manning sand-bagged checkpoints surrounding Douma's narrow streets, where shops and markets were reopening, looked bored and relaxed.

Kofi Annan, the UN-Arab League envoy, returns to Damascus in the next couple of days to attempt to give more substance to the so-called ceasefire that began on 12 April. This now looks like a critical visit, as the Houla slaughter makes Syria once again the centre of international attention and a possible target for some form of foreign intervention.

The ceasefire was only sporadically implemented from the beginning. The government has always had more interest in its successful implementation, which would stabilise its authority, than the insurgents, who need to keep the pot of rebellion boiling. The UN monitoring team says that during the ceasefire "the level of offensive military operations by the government significantly decreased" while there has been "an increase in militant attacks and targeted killings". But any credit the Syrian government might be hoping for in showing restraint will disappear if the latest atrocities are confirmed.

Not that anybody in Syria expects a quick solution to the crisis in which a mosaic of different interests and factions are battling to control the country. "My picture of Syrian society is that 30 per cent of people are militantly against the government, 30 per cent are for them, and 40 per cent don't like anybody very much," said a Christian in Damascus. A diplomat said people are much more polarised than six months ago into pro-government, anti-government and "what I term the anti-anti government, the people who dislike the regime, but equally fear the opposition". The government has been exploiting this by targeting its non-violent opponents "so they can say it is a choice between us and guys with long beards. People want change, but they are frightened it might be for the worse".

Conversations with liberally minded critics of the regime in Damascus reflect these differences. "If I made even the most peaceful protest I would be immediately arrested," said one woman in frustration. "The exiled opposition leaders have not developed a serious plan to reassure the minorities [Alawites, Christians, Druze, Kurds], though they are the main supporters of the government," added a businessman whose business is collapsing, forcing him to live off his savings.

Could the present stalemate change as a result of the death of all those people in Houla on Friday? Internationally, the atrocity, if confirmed in detail, will increase pressure for foreign support for the insurgency and tighter sanctions on Syria. Weapons from Saudi Arabia are now reportedly reaching the rebels and their degree of co-ordination in the fighting at Rastan is greater than a few months ago.

The Syrian government says its has been abiding by the ceasefire except where it comes under attack. Speaking before the Houla killings, Jihad Makdissi, the spokesman for the Syrian Foreign Affairs Ministry, said: "Since we signed the ceasefire on 12 April, we have documented 3,500 violations of it by the opposition." But the bombardment of civilian areas, with the gory consequences at Houla showing on every television screen in the world, will confirm Syria's status as a pariah, from which it had been starting to emerge.

Mr Makdissi said that an earlier monitoring mission by the Arab League had been "binned" by Arab leaders because it showed that the opposition was armed and on the offensive. There is no doubt that the opposition has become militarised, but this is not surprising given the repression of peaceful protest. "What Syria needs is gradual evolution, not armed confrontation," said Mr Makdissi. "You want Syria to reform, but you impose sanctions, so there is no gas for people to cook on."

The Syrian government has been growing stronger over the past seven weeks, because the Kofi Annan plan reduced calls for international intervention. The killings at Houla have put this in doubt and will put pressure on Annan for a more substantive ceasefire plan than the present one, which saw each side abide by it only when it was militarily convenient for them to do so.

Will the latest killings have an impact on how Syrians see the struggle for power? The indiscriminate and excessive nature of government violence over the past 14 months has alienated swathes of Syrians not naturally sympathetic to revolution. "It is not just that 10,000 people have died, but the bestial way in which they died," said one well-off and secular woman in Damascus.

For all the criticism of the Annan peace mission and the 300 monitors from the UN Supervision Mission in Syria, they appear to be the only way of abating the violence. Even with an increased flow of weapons to the opposition, the government still has a great superiority in armed force. Indeed, this turns into political weakness because, as with the US in Iraq and Afghanistan, or Israel in Lebanon and Gaza, excessive use of heavy weaponry against civilians leads to a furious reaction at home and political isolation abroad.

A better-armed opposition will be too strong to be suppressed by the government, but the outcome is most likely to be prolonged civil war rather than a clear victory by either side. Sanctions have already wrecked the Syrian banking sector and are hurting the country, but they are not leading to economic collapse. Syrians feel it is a collective punishment on them all which causes little harm to the government. There is plenty of food because Syrian agriculture, the largest sector of the economy, is benefiting from two years of heavy rain after three years of severe drought. There is no tourism and hotels are empty, but this was never as important as in Lebanon or Egypt. The biggest blow has been the fall in oil exports as foreign oil companies cease operating here.

Both the government and the armed opposition have become stronger in the past six months and neither side sees much reason to compromise. It feels like the beginning of a long war.