Geneva: Syria must allow the opening of humanitarian corridors to aid those in need, a spokesman for international mediator Kofi Annan said on Friday.

"Mr Annan is aware that we don't have a perfect situation in the country at the moment," his spokesman Ahmad Fawzi said, on day two of a Syria ceasefire introduced under a peace plan drawn up by Annan.

"There are detainees that need to be released, humanitarian corridors need to be opened." There are about a million people in need of humanitarian aid, Fawzi said.

Speaking in Geneva, he said he expected a Security Council resolution on Friday that would authorise the deployment of an advance observer mission made up of "10 to 12" people and led by Norwegian general Robert Mood as soon as possible.

If the ceasefire holds, "then the Council could authorize a full-fledged observer mission with all the capacity needed to support on the ground the implementation of the six-point plan."

The spokesman said work was being carried out around the clock to find the necessary number of troops -- likely up to 250 -- in the event of a full observer mission being approved.

Fawzi said he was not able to list the potential countries involved, but that they had been discussed with the Syrian authorities during an assessment carried out by Mood on a visit to the country last week.

"There are countries acceptable to the host country," said Fawzi. "They could come from Asia, Africa, from Latin America, South America."