U.N. chief to Syria's al-Assad: 'Stop killing your people' NEW: The town of Zabadani is under siege, opposition sources there say Ban Ki-moon calls on Bashar al-Assad to "Stop the violence. Stop killing your people State media: Al-Assad grants amnesty to all crimes committed by anti-government protesters Five people are killed in a roadside bomb explosion, the opposition says (CNN) -- Syria's President Bashar al-Assad must "stop killing" his people, the head of the United Nations demanded Sunday, as a fact-finding mission to determine whether the Syrian government is abiding by an agreement to end the violence nears a conclusion. Today, I say again to President Assad of Syria: Stop the violence. Stop killing your people," U.N. Secretary-General Ban Ki-moon said during a conference in Lebanon. The path of repression is a dead end. Ban's call comes the same day that al-Assad granted amnesty to anti-government demonstrators for "all crimes committed" since the uprising began last year, according to Syrian state-run media. Violence continued in Syria Sunday, opposition groups said. The Syrian Observatory for Human Rights said five people were killed by a roadside bomb in Idlib province, while the Local Coordination Committees of Syria said the town of Zabadani was besieged by government forces. Fares Mohammed of the LCC said about 100 armored vehicles had surrounded the city for three days, and that water, electricity and internet access had been cut off while the city was suffering temperatures below freezing. A member of the Free Syria Army -- composed mostly of deserters who are siding with the opposition -- said there were about 70 lightly armed fighters in the city. The fighter asked not to be named for security reasons. "The situation is very bad the siege is choking us and even air is running out," the fighter said, adding that fighters were setting up roadblocks to try to keep government forces out of residential areas. Hundreds of people flooded the streets of Zabadani when Arab League observers arrived, demanding the downfall of the al-Assad government, the Syrian Observatory said. At least seven people were killed in Syria by government forces Saturday, said the Syrian Revolution General Commission on Sunday. The commission is an umbrella coalition of dozens of opposition groups across the country. CNN cannot verify accounts of what is happening in Syria because the government restricts the activity of journalists. The amnesty decree follows the recent release of 5,000 prisoners by the Syrian government under a deal struck with the Arab League to release those detained during a crackdown on anti-government demonstrators. Al-Assad's decree, according to the state-run Syrian Arab News Agency, grants general amnesty for crimes committed between March 15, 2011, and January 15, 2012. Fugitives must hand themselves in by the end of the month to benefit from the amnesty, SANA reported. It applies to people who engaged in peaceful demonstrations, carried or possesses unlicensed weapons or ammunition and draft evaders, SANA said. It is the second time al-Assad has granted a general amnesty to protesters, who have been calling for an end to the regime. Al-Assad agreed to an Arab League initiative in December that called for an end to the violence against protesters, the withdrawal of troops and tanks from cities and residential areas, and the release of prisoners. As part of the agreement, the Arab League has sent observers to Syria to determine whether al-Assad's government was abiding by the agreement. The fact-finding mission, which began December 26 and is expected to conclude on January 19, has been mired in controversy, from the choice to head the Arab League mission -- Lt. Gen. Mohammed Ahmed al-Dabi, once the head of Sudan's military intelligence -- to reports that the Syrian government was limiting access. Reports of carnage mount every day despite the presence of Arab League observers in the country and international calls for al-Assad to step down and end the crackdown. Seventeen members of al-Assad's security forces who were killed in the line of duty were buried Saturday, SANA reported. Al-Assad, who has characterized the anti-government protesters as "armed gangs," says his security forces are battling terrorists intent on targeting civilians and fomenting unrest. Meanwhile, the Syrian Observatory also reported that three people died Saturday in the opposition stronghold of Homs, among them a 13-year-old child, and another in Idlib. All died of gunshot injuries, the observatory said. About 20 members of the security forces were wounded or killed in clashes with groups of army defectors in Homs, the group said. The observatory also said security forces opened fire to disperse protesters who went to meet Arab League monitors in the city of Saraqeb in Idlib province. More than 5,000 people have died since mid-March, the United Nations has said. CNN's Salma Abdelaziz contributed to this report.