Lam and police chief Stephen Lo visited the Kowloon Mosque a day after protesters took over roads and vandalised property across Kowloon as the unrest, sparked by opposition to a since-withdrawn extradition bill, entered its 20th straight weekend, reports the South China Morning Post.
The police came under fire after the water cannon truck stopped and sprayed a solution laced with blue dye over the mosque's entrance and front steps.
Lam and Lo met members of the Islamic Trust, a local community group, at the mosque. When she left after a 25-minute meeting, onlookers chanted "Five demands and not one less" and "Shame on Carrie Lam".
Said Uddin, secretary of the trust, said: "The chief executive and police commissioner said, 'a mistake has been done and we are sorry for that'.
"And we accept (that), because what's done is done... and they will not repeat it."
The fund's chairman, Zoheir Tyebkhan, said: "They sincerely apologised, and said it was not intentional."
He added that the group would urge calm among the local Islamic community.
On Sunday, thousands of protesters participated in an unauthorized march in Hong Kong to denounce the recent anti-mask law, during which roads were blocked, fires lit and Molotov cocktails were hurled at a police station.
Apart from echoing the main demands of the protest movement, which has been continuing since June, the front also called on the government to abolish the anti-mask law it brought it earlier this month.
The law stipulates a penalty of jail for up to one year and a fine up to HK$25,000 ($3,200) for wearing any face covering at a public gathering.
( With inputs from IANS )