Pakistan's Express News media group office attacked
The office of the Pakistani media group Express News in Karachi has come under attack, the group says.
Express News says gunfire and at least two explosions were heard. Three people have been injured, it reports, but guards prevented "unidentified men" from entering the building.
Journalist Jahanzaib Haque tweeted that he saw two white flashes outside his window and heard a "hail of fire".
Two people were wounded in a shooting attack outside the offices in August.
Monday's incident happened at approximately 19:15 local time (14:15 GMT).
The BBC's correspondent in Karachi, Shahzeb Jillani, says the explosions heard may have been from hand grenades.