Six people were killed and more than 20 others wounded on Wednesday when a mortar shell struck a bus carrying workers of the state-run Scientific Research Center in the capital Damascus, the state-run SANA news agency reported. The mortar was fired by armed \"terrorists\" at the Damascus\' district of Barzeh Wednesday morning and struck the worker bus, SANA said, adding that the attack also led to big material losses. The opposition activists said that the Barzeh area was subject to intense shelling coupled with intense fighting between the government troops and the armed rebels. Activists also reported heavy government troops\' shelling on several rebellious suburbs in the southern rim of Damascus. Witnesses said heavy black smoke blowing over the southern part of Damascus countryside. In the central province of Homs, the state-run media said the army had inflicted hefty tolls among the armed rebels during a series of operations carried out against rebels\' strongholds in the city. The army on Monday recaptured the strategic district of Khalidieh in Homs and apparently pressed forward to take over other rebellious areas in the restive province. However, activists\' networks said the rebels in Homs were fending off the government troops\' attacks and killing many of them. According to the United Nations report, more than 100,000 people had been killed in Syria\'s 28-month crisis, with about 1.7 million forced to seek refuge in neighboring countries.