To which derived verbal form does «نُطَاعِنُ» belong?

ʿAmr ibn Kulthūm: Address to Abā Hind, Tribal Pride and the Mill of War (Verses 23–38)

• Form II (tafʿīl)
• Form X (istifʿāl)
• Form III (mufāʿalah)
• Form VIII (iftiʿāl)