Armed police descended on a town centre after a melee - which left one man in hospital and two in police cells.
A 41-year-old man was rushed to hospital by paramedics after being stabbed in the busy White Rock shopping area in Hastings on Thursday afternoon.
Police officers are asking anyone who saw the attack, in Robertson Street, to come forward to help with their investigation.
Plain-clothed officers carrying rifles and pistols were spotted in nearby streets to make sure there was no risk to the public.
A spokesman for Sussex Police said: "A 59-year-old man from Hastings was arrested on suspicion of grievous bodily harm with intent.
"A 46-year-old woman from Hastings was arrested on suspicion of assault causing actual bodily harm.
"They both remain in custody and an investigation is ongoing."
Witnesses or anyone with any information or footage is asked to contact police online or call 101 quoting serial 978 of 12/09.
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