A loud explosion was heard in southern countryside of Syria\'s capital Damascus on Tuesday, the activists\' Local Coordination Committees reported. The report spelled no further details but said heavy dark smoke was bellowing the area, which is a battleground in the country\'s 28-month crisis. Another activist group, Damascus Media Office, said that the powerful blast rocked the Yarmouk area in southern Damascus. Yarmouk is the main camp of Palestinian refugees in Syria despite the fact that more than half of its inhabitants are Syrians. The state media has yet to report the incident, but pro- government news websites speculated that the blast was heard at the southern district of Midan, also close to Yarmouk. It added that further details are still forthcoming.