Story highlights Bana Alabed, 7, has been tweeting about the horrors of war in Aleppo, Syria

On Monday she wrote a "goodbye" message asking people to pray for her family

(CNN) Bana Alabed, a 7-year-old Syrian girl who has captured the world's attention with heartbreaking Twitter posts about the bombing of her native Aleppo, posted a message Monday asking people to pray for her and saying goodbye.

The tweet, coming as conditions inside besieged eastern Aleppo become ever more desperate, prompted deep concern for her welfare.

Under attack. Nowhere to go, every minute feels like death. Pray for us. Goodbye - Fatemah #Aleppo — Bana Alabed (@AlabedBana) December 5, 2016

It followed a foreboding previous message posted Sunday on the Twitter account Bana shares with her mother, Fatemah: "We are sure the army is capturing us now. We will see each other another day dear world. Bye.- Fatemah #Aleppo"

The account was later deleted , with no explanation. But then it came back online with a disturbing update.

"Under attack. Nowhere to go, every minute feels like death. Pray for us. Goodbye - Fatemah #Aleppo," it said.