BAGHDAD (Reuters) - An Iraqi Shi'ite militia fighting in Syria on the government's side has sent more than 1,000 extra fighters to southern parts of Aleppo over the past two days to reinforce its positions, the group's spokesman Hashim al-Moussawi said on Wednesday.

The group, Harakat al-Nujaba, is fighting alongside the Syrian army, the Lebanese Shi'ite group Hezbollah, Iranian forces, and other militias against insurgents battling to topple President Bashar al-Assad.

An advance by pro-government forces on Sunday to the south of the city resulted in the encirclement of the opposition-held half of the city. Moussawi said extra fighters were sent to reinforce areas captured from Sunni Islamist groups.

"More than 1,000 fighters from Harakat al-Nujaba’s elite forces were sent to Aleppo to help hold the ground,” he said.

Syria's military could not immediately be reached for comment.

(Reporting by Ahmed Rasheed; Writing by Angus McDowall/Tom Perry; editing by Ralph Boulton)