Arsonists have set a July memorial monument at Khagrachhari Government College, with police arresting a former leader of the now-banned Bangladesh Chhatra League (BCL) over alleged involvement.
The arson took place at around 9:30 pm on Friday, Khagrachhari Sadar Police chief Md Kai Kislu said.
He added that the rain and the monument's iron construction meant the fire caused little damage, reports bdnews24.com.
Leaders of the Awami League, which is banned from political activities, later circulated videos of the incident on social media.
The footage shows a masked man pouring a petrol-like flammable liquid from a plastic bottle around the monument before setting it alight.
Police recovered the bottle from the scene.
Night guard Senmoy Tripura said two young men entered the college around 9:30pm, claiming they had organisational work.
Shortly afterwards, flames were seen engulfing the memorial, he added.
Jahid Hasan, an activist of the 2024 Anti-discrimination Student Movement, blamed fugitive members of the banned BCL.
"By carrying out this attack, they have once again exposed their militant activities and are plotting to create anarchy across the country," he said.
Police arrested former district BCL senior vice-president Md Rony in Sabujbagh early on Saturday.
He is the elder brother of district BCL President Monir.
Officer Kai Kislu said police would file a case over the incident.