At least 67 people were killed in Syria on Tuesday, activists said, with the continued violence threatening the future of a United Nations observer mission overseeing a peace plan.

"There are many obstacles, and the Syrian government is not helping to ease them off, which delays the movement of the team to prepare the ground for the larger batch of observers to arrive in Syria," a western diplomat based in Syria told DPA, on condition of anonymity.

The head of the five-member team in Syria, Moroccan Colonel Ahmed Himmiche told reporters in Damascus that the mission "is not easy and it will require coordination with all sides."

According to Damascus-based UN spokesman Khaled al-Masri, "the team will continue talks with Syrian officials Tuesday and will not move out of the capital."

The UN Security Council has demanded full access for the team, but there are fears that the government will try to hinder the mission by forcing observers to travel with government minders.

The Arab League earlier this year pulled out an observer mission over escalating violence.

Representatives of the Syrian opposition meeting in Moscow said they were skeptical about the peace plan of UN-Arab League envoy Kofi Annan.

"It is not the best option, but the lesser evil," said Haitham Manna from the National Coordinating Committee for Democratic Change. He said that a dialogue with the leadership in Damascus was almost impossible. Manna said: "Al-Assad has made Syria a slaughter house."

Under Annan´s plan, Damascus was to withdraw its troops and heavy weapons from restive areas across Syria after a ceasefire and start a dialogue with the opposition.

In Luxembourg, UN Secretary General Ban Ki-moon has asked the European Union if it could put planes and helicopters at the disposal of the observers to enhance the "mobility of the mission."

French Foreign Minister Alain Juppe called Tuesday for international sanctions against Syria to be strengthened, saying measures already in place were hitting the mark.

Speaking at a working meeting in Paris to assess the effectiveness of the sanctions Juppe said: "We must keep up pressure on the Syrian regime. That means reinforcing sanctions, which have an impact on the Syrian authorities."

Though the level of violence Syria has dropped since the truce took effect on April 12, government forces have continued shelling rebellious areas.

The Local Coordination Committees, which documents violence on the ground, said that 35 people were killed in the northern province of Idlib, most of the bodies were for people who are believed to have been killed in shelling on Monday, but were recovered and identified on Tuesday.

Troops and rebels clashed in the southern province of Daraa, near the Syrian-Jordanian border, opposition activists said. Activists said six people were killed in Daraa. Others were killed in the central provinces of Homs and Hama.

"The fighting is concentrating in an area called al-Jaat and Basr al- Harir. The government forces are trying to storm the area where rebels have strongholds, but all their attempts have so far failed," Rami Abdul-Rahman, head of the Britain-based Syrian Observatory for Human Rights, told dpa.

Russia, Syria’s main ally, criticized "foreign forces" as an obstacle to peace efforts in Syria and called for speeding up the deployment of the UN mission.

"There are countries and external forces that are not interested in the success of the current efforts by the UN Security Council, which have been trying to replace the (council) with various informal formats, such as groups of Syria´s friends, persuading the opposition not to cooperate with the government in any matter, including measures to enforce a truce," Foreign Minister Sergei Lavrov said, according to the Itar-Tass news agency. (© Copyright 2012 Ha´aretz 04/18/12)