Heavy fighting erupted Sunday between Syrian troops and rebels on the outskirts of the capital - Damascus, reported an opposition group. The clashes occurred at a security checkpoint in the suburban area of Kafr Soussa, said the London-based Syrian Observatory for Human Rights. The organization did not give casualty figures, according to a report of DPA. Several blasts were meanwhile heard in the area of Douma near Damascus, reported the observatory. The explosions were caused by shelling attacks mounted by Syrian troops against the area, it added.