A petrol bomb was hurled at theHindu Munnani office here by some unidentified people, sparking tension in the city.The incident comes days after two mosques in the city were targeted in a suspected retaliation for the attack on a Hindu Munnani functionary here.The matter came to light after the staff, who opened the office at 10 AM noticed broken pieces of a bottle which contained molotov cocktail, police said.On information, senior police officials, including DCP (Law and Order), Balaji Saravanan rushed to the spot and held inquiry.Police are also verifying the surveillance cameras in the vicinity to get clue about the miscreants, with finger print experts pressed into service, they said.