Three students have been arrested after three other students were attacked with knives and injured outside a school in Khon Kaen on Tuesday evening.
The attack outside the fence of Nampongsuksa School was reported about 5.30pm.
Police said three schoolboys sustained knife wounds and were rushed to hospital.
The wounded students were all in Matthayom Suksa 5 (Grade 11) at the school.
Two of them had serious injuries. They were stabbed in the abdomen and the lungs. The third had a knife wound to his left chest.
They were attacked by students in Mathayom Suksa 3 (Grade 9) at the same school.
Police later arrested the three junior students involved in the brawl - Mathayom Suksa 3 students at the same school and identified only as Chao, Phum and Oak.
Police also seized from them a knife with a 15cm blade.