2 judicial officials assassinated in Syria Two judicial officials were assassinated Sunday in Syria's Idlib province, and the strife-riven nation faced what could be a critical week, almost a year after the bloody rebellion erupted against the government of President Bashar Assad. Authorities said "an armed terrorist group" in Idlib city opened fire on a car carrying a judge, Mohammed Ziyadeh, and a prosecutor, Nidal Ghazal. Also killed was the driver, said the official Syrian Arab News Agency. An opposition activist reached in Idlib contradicted the official version and said Syrian security forces killed the pair because they were cooperating with antigovernment rebels active in the northwestern region, close to the border with Turkey. Assassinations by unknown assailants have become a familiar feature of the conflict in Syria, where armed insurgents are fighting to oust Assad, whose family has ruled the country for more than 40 years. On Saturday, the state news agency reported, gunmen assassinated a member of the city council in the northern municipality of Aleppo, a business hub that is regarded as staunchly pro-Assad. In various areas of Syria, the government has been fighting to recapture terrain lost to rebels. The opposition said insurgent enclaves in the western city of Homs were shelled again Sunday, as reports circulated that ground troops might be preparing an assault on the besieged rebel bastion of Bab Amr. The Local Coordination Committees, an opposition coalition, reported at least 20 killed Sunday across the country, including nine in Homs. The numbers could not be independently confirmed because of restrictions on media access in Syria. Despite the ongoing violence and threat of a full-fledged civil war, Assad has scheduled a nationwide referendum for Sunday on a new draft constitution that is a centerpiece of his asserted reform agenda. Much of the opposition has rejected the move as a stalling tactic and called for a boycott. Meantime, Arab and other nations calling for Assad to cede power are scheduled to meet Friday in Tunis, Tunisia, to discuss new ways to put pressure on the embattled Syrian president. Diplomats from the United States, Turkey, Saudi Arabia, Qatar and other allied nations have pledged to ramp up assistance to Syria's opposition, which remains deeply divided. Diplomats, however, say any international intervention remains off the table in Syria, where a popular revolt against Assad began 11 months ago. A request this month by Arab foreign ministers that a joint Arab-U.N. peacekeeping team be dispatched to Syria was denounced by the Assad administration as a "hostile act" and "a call for foreign intervention in Syrian affairs." Assad has said he has no intention of resigning and has vowed to restore security and implement wide-ranging political reform leading to a representative democracy. Many opponents say only Assad's departure will be enough. Russia and China, which vetoed a pair of United Nations Security Council resolutions condemning Assad's crackdown on dissent, have applauded the plans for a referendum on the new constitution. The opposition says a peaceful protest movement gravitated to arms in response to brutal repression. The government says armed Islamic militants have been part of a foreign "conspiracy" to topple Assad since the outset of trouble. On Sunday, opposition sympathizers reported a heavy police presence in Damascus' Mezzeh district, a day after the neighborhood hosted what activists called the largest protest march to date in the capital. "There are almost no people on the street," said an activist reached via Skype, who, like others, declined to give his name for security reasons. The opposition has accused authorities of shutting down roads, rerouting bus lines and cutting off communications and services in a bid to isolate anti-Assad strongholds in the Damascus suburbs and elsewhere. Troops have also been dispatched to quell protests and arrest alleged rebel sympathizers, the opposition says. "There are snipers now, and no one can leave the house," said an activist Sunday in the Damascus suburb of Barzeh, a frequent site of antigovernment marches.