Floundering buy now, pay later player Sezzle rocketed 95.8 per cent on Wednesday to finish the day in a trading halt as the market operator ASX sought an explanation for the extraordinary price action.

After months of heavy falls, the junior buy now, pay later sector posted huge gains across the board, with Zip Co climbing 20.1 per cent, Laybuy jumping 79 per cent, and Openpay surging 31.4 per cent.