The Syrian army on Monday heavily shelled the dissident city of Homs, which the opposition has dubbed a "disaster area", dpa reported.
"The shelling intensified throughout the night and the early hours of Monday in Baba Amr (a neighbourhood in Homs)," Omar Idlibi, a Syrian activist based in Lebanon, told dpa.
He said around 23 people have been killed in Homs since Sunday, including 16 in the Baba Amr.
Meanwhile, online opposition activists called Homs a "disaster area" that lacks all living necessities.
"There are no food supplies inside the city - no water and no electricity," Idlibi added.
"The city is under siege, with 76 military checkpoints set up to monitor the movement of people," he said.
Homs is a focal point in protests against the regime of President Bashar al-Assad.