At 20.35pm, a bomb was thrown into a PTT petrol station in tambon Nong Hoi, Muang district. Four people, three of whom were petrol station staff, were injured. The other injured was a woman who came to the station to fill up her car. They were rushed to a nearby hospital.
At 21.35pm, two grenades were hurled into the office of Boon Rawd Brewery Co in tambon Yang Nerng of Sarapee district. One of them exploded but the other did not go off.
The third bomb attack took place at 22.15pm at a parking lot of Andaman Seafood Restaurant in tambon Pa Dad, Muang Chiang Mai district. Two cars were damaged and no injuries were reported.
Police said the bomb was hidden under the wheel of a car.
Police were investigating.