The Syrian army said Saturday that dozens of its soldiers had been killed in a major attack led by Islamist Hayat Tahrir al-Sham rebels who swept into the city of Aleppo, forcing the army to redeploy in the biggest challenge to President Bashar Assad in years.

Russia¡¯s Defense Ministry said its air force had carried out strikes on Syrian rebels in support of the country¡¯s army, Russian news agencies reported. The strikes followed what was the boldest rebel assault for years in a civil war where front lines had largely been frozen since 2020.

Hayat Tahrir al-Sham (HTS), once known as the al-Nusra Front, is designated a terrorist group by the U.S., Russia, Turkey and other states. Assad is a close Moscow ally.