Valmiki Ramayana Yuddha Kanda Sarga 44 Shloka 3

दारुणे fierce, तस्मिन् them, तमसि darkness, राक्षसःअसि thinking to be Rakshasa, इति thus, हरयः monkeys, हरिश्च and monkeys, असि thinking to be, इति thus, राक्षसाः Rakshasa, समरे fought, अन्योन्यम् one another, जघ्नुः hit .

In the fierce darkness that prevailed, monkeys hit monkeys thinking to be Rakshasas and Rakshasas hit Rakshasas thinking to be Vanaras (not knowing in darkness) hit each other.