Syria unrest: Renewed clashes as UN monitors due Published duration 15 April 2012

media caption Activist Sami Ibrahim says shelling is continuous'. His footage has not been independently verified.

Fresh clashes have erupted in Syria as a vanguard of UN monitors prepares to arrive to oversee the shaky ceasefire.

Activists said there was heavy shelling in the city of Homs, while rebel fighters reportedly attacked a police station in Aleppo province.

Syrian state media claim that attacks by "terrorists groups" have intensified since Thursday's truce.

The United Nations passed a resolution on Syria on Saturday, authorising the deployment of unarmed observers.

A spokesman for international peace envoy Kofi Annan said that an advance party of six observers would arrive in Syria on Sunday evening and would "be on the ground in blue helmets tomorrow [Monday]".

Ahmad Fawzi said the six would be "quickly augmented by up to 25 to 30 from the region and elsewhere".

A ceasefire came into effect on Thursday morning but there have been many violations since, and the BBC's Jim Muir in Beirut says the monitors will arrive to find a truce in dire need of reinforcement.

On Sunday, the UK-based Syrian Observatory for Human Rights reported heavy shelling in the Khaldiyeh and Bayada districts of Homs. Three people have died in that shelling, the Observatory says.

One Khaldiyeh activist told Reuters: "Early this morning we saw a helicopter and a spotter plane fly overhead. Ten minutes later, there was heavy shelling."

There were also reports of heavy machine-gun fire from Syrian troops.

The Observatory also said there were explosions and gunfire as rebels attacked a police station in the town of al-Bab in northern Aleppo province.

Activists say 32 people have been killed since the ceasefire came into effect.

Media cannot operate freely in Syria and there is often no verification of casualty reports.

Our correspondent says the rebels and government are bitterly blaming one another for the violations.

He says the advance party of UN observers will examine how to operate in such an environment.

They will look at how to coordinate with the Syrian authorities, how freely they will be able to move around and how safe the situation will be.

If successful, UN Secretary General Ban Ki-moon says he will make firm proposals in days for a larger group of about 250 monitors.

He said the UN would need complete freedom of movement for its monitors.

A UN spokesman, Kieran Dwyer told the BBC: "The Security Council envisages that they'll have full access and indeed that nobody should suffer any adverse consequences by talking to any of the military monitors."

Although the levels of violence in general are lower than pre-ceasefire Syria, the government has still to conform to one key element of the six-point peace plan that requires the withdrawal of tanks from towns and cities.

media caption UN Secretary General Ban Ki-moon: "The whole world is watching with sceptical eyes"

Saturday's UN resolution was passed after Russia approved a revised text.

But US ambassador to the UN Susan Rice said the continuing violence raised "renewed doubts about the sincerity of the [Syrian] regime's commitment to the ceasefire".

The British Foreign Secretary, William Hague, said the team of 30 observers authorised to enter Syria was not enough to monitor what was going on in the whole country and would need to be "beefed up". But, he said, the Annan plan was "better than any alternative scenario at the moment which involves death and violence".

The peace plan, drawn up by Mr Annan, who is the envoy for the UN and Arab League, aims to end more than a year of violence in Syria which the UN says has killed more than 9,000 people, mostly civilians.