BEIRUT (AP) - Six days of fighting in a Damascus suburb has killed more than a hundred people and possibly many more, activists said Monday, in what the government also acknowledged may be a dramatic spike in the rising death toll in Syria. The reports came as President Bashar Assad's forces pressed on with a major offensive against rebels closing in on parts of the Syrian capital, and while government troops moved to encircle the contested town of Qusair near the Lebanese border. The precise number of those killed in the latest fighting in the Jdaidet Artouz and Jdaidet al-Fadel districts could not be immediately confirmed. The two adjacent neighborhoods are around 15 kilometers (10 miles) southwest of Damascus. The Britain-based Syrian Observatory for Human Rights said the death toll, mostly due to shelling, could be as high as 250. Rami Abdul-Rahman, who heads the Observatory, said the group has documented 101 names of those killed, including three children, 10 women and 88 men, but he fears a much higher toll. The dead included 24 rebels, he added. The Local Coordination Committees, another activist group, put the death toll at 483. It said most of the victims were killed in Jdaidet Artouz. State-run news agency SANA said Syrian troops had "inflicted heavy losses" on the rebels in the suburbs. A government official in Damascus told The Associated Press that rebels were behind the "massacre" in Jdaidet al-Fadel, saying they sought to blame government forces who entered the area after the killings occurred. "The army discovered the massacre after entering the area," the official said on condition of anonymity in line with regulations. The corpses were already decomposed, he added. Jdaidet al-Fadel is mostly inhabited by Syrians who fled the Golan Heights after the area was captured by Israel in 1967. Jdaidet Artouz has a large Christian and Druse population. Mohammed Saeed, an activist based near Damascus, said rebels withdrew as soon as the government offensive began last week. After that, he said via Skype, troops and pro-government gunmen stormed the area and killed some 250 people. "The situation is very tense," Saeed said, adding that the area has no electricity, water, or mobile phone service. There is widespread destruction in Jdaidet al-Fadel including its only bakery. Reports of death tolls in Syria's civil war often conflict, especially in areas that are difficult to access because of the fighting. The government also bars many foreign journalists from covering the conflict. Both activist groups, the Observatory and the LCC, rely on a network of activists on the ground in different parts of Syria. In August, activists said days of shelling and a killing spree by government troops left 300 to 600 dead in the Damascus suburb of Daraya, just north of Jdaidet al-Fadel. The main opposition group, the Cairo-based Syrian National Coalition described the killings as "the latest heinous crime committed by the Assad regime." It added in a statement that "the deafening silence of the international community over these crimes against humanity is shameful." British Foreign Secretary William Hague said the reports of the massacre underline the urgent need to bring Syria's war to an end. "I am appalled by the reports of the killing by Syrian Government forces of dozens of people, including women and children, in the town of Jdaidet Al-Fadel, a suburb of Damascus," Hague said in a statement. This is yet another reminder of the callous brutality of the Assad regime and the terrible climate of impunity inside Syria. Also Monday, two bombings targeted an army checkpoint and a military post in a third Damascus suburb, Mleiha, killing eight soldiers there, according to the Observatory. The army also pressed on with its offensive near the Lebanese border, where it has been pushing for two weeks to regain control along with the help of a Hezbollah-backed militia known as the Popular Committees. The region is strategic because it links Damascus with the Mediterranean coastal enclave that is the heartland of Assad's Alawite sect, an offshoot of Shiite Islam. The fighting around Qusair also points to the sectarian nature of the Syrian conflict, which pits a government dominated by the president's Alawite minority against a primarily Sunni Muslim rebellion, and underscores widely held fears that the civil war could drag in neighboring states. The pro-government daily Al-Watan predicted Monday that "the liberation" of the area will be completed within a "few days." Troops have already captured several towns and villages around Qusair. The report claimed the army was making a "rapid" advance in the outskirts of Qusair, inflicting heavy losses on the rebels and forcing some of them to retreat toward Lebanon. In Lebanon, there are deep divisions over the Syrian conflict, with Lebanese Sunnis mostly backing the opposition while Shiites support Assad. Lebanese fighters have also traveled to Syria to join either Sunni or Shiite groups, and several have been killed in clashes. Over the weekend, several rockets fell in the predominantly Shiite Lebanese towns and villages along the border and some Lebanese schools in the area remained closed Monday for fear of more shelling. Syria's conflict started with largely peaceful protests against Assad's regime in March 2011 but eventually turned into a civil war. More than 70,000 people have been killed so far, according to the United Nations.