At least 20 people were killed and over 200 wounded on Saturday by fresh Syrian military shelling against a rebel-held district east of the capital Damascus, a monitor group reported.The Syrian forces fired artillery and shells as well as surface-to-surface missiles into the suburb of Douma, a main bastion for rebel groups in the Eastern Ghouta countryside of Damascus, the Syrian Observatory for Human Rights reported.The death toll could rise due to the large number of critically wounded people, the Britain-based watchdog group added.Last week, Syrian airstrikes against Douma killed 82 people, according to the Observatory.Douma has emerged as the main stronghold of an array of jihadist groups in eastern Damascus, mainly the Islamic Army, throughout the country's long-running conflict.Reports said the Syrian army has mounted the offensive against Douma after the leader of the Islam Army, Zahran Alloush, attacked a key military position in the nearby suburb of Harasta.