The head of the UN observers' mission in Syria demanded Sunday that warring parties allow the evacuation of women, children, elderly and sick people endangered by the fighting in the besieged city of Homs and other combat zones.

Maj. Gen. Robert Mood said the observers had been trying for the past week to extricate civilians and the wounded from the central city of Homs but had failed because neither government troops nor the rebels were willing to hold their fire.

"The parties must reconsider their position and allow women, children, the elderly and the injured to leave conflict zones without any preconditions and ensure their safety," Mood said in a statement. He said the UN will attemp to "extract civilians from the line of fire over the past week have been unsuccessful," he added.

His call follows a statement by activists who say conditions in the central city of Homs, which has been bombarded for more than a week by Syrian forces, are growing more dire. The groups are pressing for the evacuation of 1,000 endangered families and dozens of wounded people who can't get adequate help.

Homs has been under siege for a week, part of a major escalation of violence around the country that forced the 300-strong UN observer force in Syria to call off its patrols.

"The humanitarian situation in Homs is very difficult," said Rami Abdul-Rahman, who heads the British-based activist group Syrian Observatory for Human Rights Observatory. "It is very clear that the army wants to retake Homs."

The Observatory asked the UN on Saturday to intervene in the violence in Homs and evacuate more than 1,000 families, including women and children, whose lives are in danger. It also said dozens of wounded people in rebel-controlled areas cannot get medicine or doctors to treat them.

Mood recently spoke about the suspension of his mission in Syria saying that intensifying clashes over the past 10 days were "posing significant risks" to the unarmed observers who were spread out across the country, and impeding their ability to carry out their mandate. The observers' decision came after weeks of escalating attacks, including reports of several mass killings that have left dozens dead.

Demonstrators in Houla, near Homs, protest against the Assad regime. (Shaam News Network/Reuters)

The observers have been the only working part of a peace plan brokered by international envoy Kofi Annan, which the international community sees as its only hope to stop the bloodshed. The plan called for the foreign monitors to check compliance with a cease-fire that was supposed to go into effect on April 12, but they have become the most independent witnesses to the carnage on both sides as government and rebel forces have largely ignored the truce.

Assad regime 'committing more crimes as revenge'

The statement calling off observer patrols reinforced fears that Syria is sliding ever closer to civil war 15 months after the rebellion to oust Syrian President Bashar Assad began. Opposition groups say more than 14,000 civilians and rebels have been killed since the uprising began in March 2011.

In Turkey, the leader of Syria's main opposition group, Abdulbaset Sieda, said in a speech that the suspension of the observers' activities shows that "the international community has given up hope on this regime that is in its last days." He added that Assad's government has lost control over many large areas and "it's now suffering from confusion and committing more crimes as revenge."

The Syrian government has been waging a fierce offensive through towns and villages nationwide for the past week, trying to pound out rebels by shelling urban areas with tanks and attack helicopters.

Rebels also have attacked Syrian forces, mostly trying to burn out their tanks.

Britain's Foreign Secretary William Hague said that the development only underscores the need for the international community urgently to come together to compel the regime to meet its commitments.\

The US reiterated its call for the Assad regime to comply with the plan, "including the full implementation of a cease-fire."

The Observatory and the Local Coordination Committees, another activist group, also reported intense clashes between rebels and troops in the Damascus suburb of Mleiha over the weekend. The LCC said four people from both sides were killed in the fighting.

Rebels also attacked an army checkpoint in central Hama province killing at least three soldiers, the Observatory said. Both groups also reported violence in the northern provinces of Idlib and Aleppo as well as the eastern region of Deir el-Zour and the southern province of Daraa.

The LCC said at least 20 people were killed Sunday while the Observatory put the number at 14.