Violence has ramped up in several parts of Syria claiming the lives of many people, as the Arab League (AL) observers started their work on Tuesday as part of AL's efforts to end the bloodshed in Syria.

Syrian security force members inspect the damaged cars at a suicide blast site in Damascus, Syria, on Dec. 23, 2011. Two suicide bombers blasted two security centers in central Damascus on Dec. 23, leaving about 40 people dead and over 150 others injured. [Xinhua]

About six Syrian workers were killed when their bus was blown up by two explosive devices that went off on the highway that connects coastal Latakia province with northern Aleppo city, state- run SANA news agency reported.

SANA said the explosives were planted by "terrorists," adding that the victims had been working at a textile factory and were riding in a bus back to their homes when the explosion occurred.

The explosions created two craters, each one meter in diameter, and caused considerable damage to the bus, said SANA, adding the bodies of the dead workers along with the injured ones were transported to the National Hospital in northern Idlib province.

In a separate incident Tuesday morning, Syrian authorities clashed with an "armed group" along the Turkish border and killed a number of its members. The group was trying to facilitate the infiltration of some gunmen from the Turkish territory into Syria, it said.

A military source was quoted as saying that Syrian forces killed and wounded an unidentified number of gunmen, and seized a large quantity of weapons and ammunition. Other members of the group fled towards Turkish territories, the report said.

In restive Homs province in central Syria, a gas pipeline was targeted in early hours Tuesday by an explosive device planted by "terrorist groups", SANA reported.

The pipeline was hit at 01:45 a.m. local time in the north of al-Ashrafiya village, said the report, adding that the pipeline carries gas from al-Rayan field in eastern Homs to power stations in the central province of Hama.

It noted that the pipeline remained ablaze for three hours and that firefighters were unable to reach the area.

This is the third attack on oil and gas pipelines in the country.

On Dec. 13, Syria said gunmen blew up a gas pipeline in Homs, causing minor damage. A week earlier, another oil pipeline in Homs was targeted. No injuries were reported in both attacks.

At least four pipelines have been targeted since the eruption of unrest in Syria in mid-March. Syria held what it called " saboteurs" responsible for the attacks. In July, fire damaged a natural gas pipeline in Deir el-Zour. Another oil pipeline was blasted in Talkhalakh area in Homs on July 29.

In yet a murky awkward incident, a medical engineering student opened fire at his colleague during mid-term exam Tuesday, killing a student and wounding three others, one is in critical condition, said SANA, adding that the perpetrator fled the scene and Syrian authorities are still hunting him. The student's motives are still unknown.

Meanwhile, according to the Cairo-based AL operation room, the first batch of AL observers, led by Sudanese General Mohammed Ahmed Mostafa al- Dabi, arrived in the restive Syrian city of Homs earlier in the day and already started their job.

Given the sensitivity of the issue, AL chief Nabil al-Arabi Tuesday urged media outlets to be very accurate while reporting the observers' mission, adding that media outlets should broadcast true stories, according to official news agency MENA.

Besides, Syria's SANA said the observers had met with Ghassan Abdul-Al, the governor of Homs, along with some residents of the restive province.

It said the group went to Bab Amro, a hotbed of armed clashes with the government forces, in addition to other areas there.

According to SANA, some of the group's members headed back to Damascus while the others remained in Homs. It spelled no further details.

The monitoring mission is to ensure the Syrian government abides by its commitment to end its crackdown on protesters under the peace plan. The AL peace plan requires the government to remove its security forces and heavy weapons from urban streets, start talks with opposition leaders and allow human rights workers and journalists into the country.

Qadri Jamil, the leader of the newly-formed "the Popular Will Party," a gathering of communist and leftist activists, told Xinhua in a recent interview that the presence of Arab observers would help to rein in violent acts in Syria, adding that his party strongly supports the Arab League initiative to end the 10-month- old crisis in the country.

"If the observers are neutral, they would help the Syrian people ... Otherwise, they could further complicate the situation, " he said.

Syria signed the AL observer protocol on Dec. 19 in the Egyptian capital of Cairo after the AL threatened to submit the issue to the United Nations Security Council.

The Syrian government said last week that a total of 2,000 army and security personnel were killed during the nine-month-old unrest. However, the United Nations said more than 5,000 Syrians have been killed.

In the meantime, the Local Coordination committees, an activist network, said as many as 26 people were killed across Syria mostly in Homs. Their report, however, couldn't be independently verified.

Opposition activists have repeatedly accused the Syrian government of violently repressing anti-government protests, but the government denied the accusation, blaming the unrest on armed groups and a "foreign conspiracy".