Islamabad , Pakistan ( CNN ) -- Police have arrested a Pakistani teenager accused of writing insulting comments about Muslim prophet Mohammed in a school exam , a senior police official said . Police arrested 17-year-old Sami Ullah in Karachi after receiving a complaint from the local board of education , said Karachi police official Qudrat Shah Lodhi . Lodhi declined to say what Ullah wrote in his high school exam for fear of violating Pakistan 's blasphemy laws himself . The controversial laws say whoever defiles the name of the prophet shall be punished by death or imprisoned for life . The laws came into sharp focus late last year when liberal Pakistani politician Salman Taseer was gunned down after leading a public campaign to change them . Taseer said the laws were being misused to persecute minorities . Ullah -- the latest Pakistani to be accused of blasphemy -- is a Muslim , according to police . He wrote the alleged blasphemous comments when taking a school exam in April 2010 , police said . It 's not clear why it took months for the board of education 's complaint against Ullah to reach police . Ullah has apologized for his comments and begged the court for leniency , police said . Journalist Nasir Habib contributed to this report .
The try ' n't say what he wrote for fear of violating blasphemy law . The law came into force after a liberal politician was killed last year . Ullah is the latest Pakistani to be accused of blasphemy . He wrote the comments during a national exam last year .