Rebels fire artillery in the latest attempt to take a vital military base near the southern city of Deraa.
The fighters are attempting to reverse recent regime gains in the south of the country.
Speaking in the Russian town of Sochi, UN Chief Ban Ki-moon urged countries to remain focused on finding a political solution to the crisis, criticizing Syrian authorities for not allowing UN inspectors to investigate claims of chemical weapons use.
(SOUNDBITE) (English) UN SECRETARY-GENERAL, BAN KI-MOON, SAYING:
"Our team, is ready at any time. Within 24 to 48 hours notice, they can immediately conduct an investigation. I again urge the Syrian authorities to be flexible and allow our teams to have an on-site investigation."
Syrian rebels complain that government forces are benefiting from Russian arms supplies, but Lavrov stressed Russia was merely honouring existing contracts.
(SOUNDBITE) (Russian) RUSSIAN FOREIGN MINISTER, SERGEI LAVROV, SAYING:
"We
