The Arabic words in yellow were found carved onto the bark of the trees from the High Court square to Bangabazar along the Fazlul Huq Hall on Friday.
But a professor of the Arabic of the university was not impressed with such writings as Arabic letters and words are considered sacred because the Holy Quran is written in Arabic.
"Names of Allah must be in sacred places. I think this is an insult to Allah's name," he added. Vagabonds loiter around the areas, according to the witnesses.
The DU authorities are unaware of the incident.
The Ministry of Religious Affairs, in May last year, used Arabic to write the caution like "Do not urinate here" and the people stopped taking a leak in front of the 'holy words'.
"I informed the city corporation as soon as I saw it," she added.
Fazlul Huq Hall Provost Prof Jashimuddn said these were sensitive writings. The authorities should investigate who have done it.
Proctor of the university Prof Golam Rabbani said they were looking into the matter.