As many as 311,897 candidates are appearing in these examinations at 250 centres in the metropolis.
According to the Controller of Examinations of the Board of Secondary Education Karachi (BSEK), Rafia Mallah, the papers began in a smooth manner.
She said that on the opening day, the papers of Islamiat/Ethics and Science were conducted.
Rafia stated that vigilance teams of the BSEK visited various examination centres in the city.
Meanwhile, the Assistant Commissioner Sub-Division Nazmiabad, Shaikh Muhammad Rafiq, visited various examinations centre on Thursday.
He also saw the facilities that have been extended to the candidates.
Rafiq also urged the teachers supervising the examinations to ensure that unfair means are not resorted to.
He also directed the police personnel on duty not to allow any unauthorised person enter into the premises.