Aid workers hoping to evacuate trapped civilians and the wounded were unable to enter hard-hit areas of the Syrian city of Homs on Thursday due to shooting and an "unclear" security situation, the International Committee of the Red Cross (ICRC) said.

Government forces and rebels had both agreed on Wednesday to an ICRC request for a truce for humanitarian reasons after more than 10 days of intense fighting.

But when a team from the ICRC and Syrian Arab Red Crescent headed to the old city of Homs on Thursday morning, they heard shots, a spokesman said. The Syrian army shelled central districts of the city on Thursday, residents said.

"After having attempted to go into the old city of Homs this morning, the team decided to turn back to Homs city due to shooting. We could not identify the source of the shooting," ICRC spokesman Hicham Hassan told Reuters on Thursday evening.
 

"Later on, the team concluded that the security situation was too unclear for us to go in," he said. "The team has now returned to Damascus."

The ICRC, the only international agency to deploy aid workers in Syria, remained in touch with government forces and opposition groups, he said.

"We will still attempt to enter the affected areas of Homs city but we cannot confirm the timing for that. Our dialogue with the parties continues," Hassan said.

Homs is the centre of the 15-month revolt against President Bashar al-Assad whose forces are intensifying efforts to crush the uprising.