A handful of UN observers resumed their tour of Syrian hot spots on Wednesday, April 25 as envoy Kofi Annan urged the fast deployment of the full, 300-strong mission and voiced alarm about persistent violence, AFP reports.

A car bomb went off in central Damascus on Tuesday, as six civilians were reportedly killed across Syria, taking to nearly 300 the number of people who have died since a tenuous ceasefire went into effect on April 12.

Annan branded the bloodshed "unacceptable" as he and world powers called for the speedy deployment of 300 observers, but a top UN official said it would take at least a month to get the first 100 in place.

Addressing the UN Security Council via teleconference, the UN-Arab League envoy said he was "concerned" about the violence surging after observers visit individual cities.

The former UN chief said Syrian President Bashar al-Assad has still not fulfilled a promise to end violence and said the situation was "bleak" and "unacceptable".

Annan said he was "particularly alarmed" at reports that government forces had entered the city of Hama after a visit by UN monitors and killed "a significant" number of people. "If confirmed this is totally unacceptable and reprehensible," the former UN secretary general told the council.