Bana Alabed disappeared from social media on Sunday after Syrian regime forces advanced into opposition-held parts in eastern Aleppo.
She, however, posted a new tweet on Monday.
“Under attack. Nowhere to go, every minute feels like death. Pray for us. Goodbye,” her mother, Fatemah, said on Twitter.
Bana, who lives in eastern Aleppo’s opposition-held Al-Qatirgi district, used to post messages on her Twitter account -- along with her mother -- about frequent aerial attacks by Syrian regime forces and Russian warplanes in the city.
She posted a tweet on Saturday about a regime attack on the war-battered city before her account disappeared from Twitter.
"We are sure the army is capturing us now. We will see each other another day, dear world. Bye," the tweet read.
Bana, who had boasted some 200,000 Twitter followers, saw her home bombed on Nov. 27, but she and her mother reportedly survived the attack.
"Tonight we have no house, it's bombed and I got in rubble. I saw deaths and I almost died," the seven-year-old tweeted at the time.
The girl had also asked her followers to pray for her and her mother amid persistent attacks by the regime and its allies.
"Under heavy bombardment now. In between death and life now, please keep praying for us," she appealed.
Since mid-November, regime forces and Russian warplanes have stepped up their attacks on eastern Aleppo’s opposition-held neighborhoods.
Since then, hundreds of civilians have been killed and thousands more injured, according to figures released by local civil defense officials.
The fierce bombardments have been accompanied by attempts by the Russia-backed Assad regime to wrest control of eastern parts of the city four years after they were captured by armed opposition groups.
Syria has been locked in a devastating civil war since early 2011, when the regime cracked down on pro-democracy protests -- which erupted as part of the "Arab Spring" uprisings -- with unexpected ferocity.
Since then, hundreds of thousands of people are believed to have been killed and millions more displaced by the conflict.