ALEPPO, Syria: Syrian government forces advanced quickly inside rebel-held east Aleppo on Monday, as the United Nations raised the alarm for nearly one million people living under siege in the war-wracked country. UN aid chief Stephen O’Brien told the Security Council that 974,080 people were now living under siege in Syria, more than double the number from six months ago. The assessment follows mounting international concern over the fate of Aleppo, where 250,000 people are trapped in the east of the city under a government siege. President Bashar al-Assad’s regime lost control of the eastern part of Syria’s second city to insurgents in 2012, and its recapture would be its biggest victory in the country’s brutal five-year conflict. Rebel forces have steadily lost ground since regime ally Russia intervened to bolster Assad’s government last year. They faced a new blow on Sunday when government forces backed by Iranian and Russian troops and fighters from Lebanon’s Shiite movement Hezbollah entered Aleppo’s Masaken Hanano district — the first neighborhood the rebels controlled in 2012.