Britain's Foreign Office says Syria's chief diplomat in London has defected, making him the latest in a series of top officials, including military officers, who have quit President Bashar al-Assad's embattled government in recent weeks.

The foreign office said Monday that charge d'affaires Khaled al-Ayoubi informed it that he would no longer represent President Assad's government.

The news came as Syrian troops and rebels continue to clash in the northern city of Aleppo, with each side claiming victory.

The government said it had overrun the district of Salahhedine and inflicted great losses against the rebels. But rebel forces said that no government troops were in the neighborhood and that fighting was ongoing.

Syrian Foreign Minister Walid al-Moallem vowed the rebels in Aleppo will be defeated. He made the comment on a visit to Iran, Syria's strongest regional ally.

At a joint news conference with Moallem, Iranian Foreign Minister Ali Akbar Salehi dismissed any hopes of a peaceful transition in a post-Assad Syria, calling them an “illusion.”