A petroleum well drill- or coiled tubing string (1, 1b) mounted fishing tool, comprising - a main body comprising a lower housing with a magnet having at least one magnet surface facing downwards in said well at a lower end of said lower housing and arranged for catching and holding undesired magnetic objects present in said well, said main body provided with a connector to said drill- or coiled tubing string (1, 1b) at its upper end, characterized by - said main body further comprising a generally cylindrical upper housing with a central channel with laterally directed curl flow forming nozzles through the cylindrical wall of said upper housing, said nozzles leading out into one or more helical grooves between helical ridges, - said magnet comprising permanent magnets (31, 32, 33, 34, 35) arranged in a magnetization pattern which concentrates their combined magnetic flux through said downwards facing surface, - said upper housing's vertical channel extending near its lower end to peripherally directed channels extending to an outer wall of said lower housing about said magnets (3, 31, 32, 33, 34, 35) and leading to axially directed peripheral nose ports at a peripheral lower end of said lower housing and arranged for flushing fluid ahead of said magnet (3, 31, 32, 33, 34, 35), - said central channel provided with a vertically displaceable cylindrical flow control sleeve which is provided with a closing seat near its lower end so as for receiving a ball for shutting off the flow to said nose ports and redirecting said flow through apertures (84, 84a, 84b, 84c) in the wall of said sleeve to said curl flow forming nozzles. - a main body comprising a lower housing with a magnet having at least one magnet surface facing downwards in said well at a lower end of said lower housing and arranged for catching and holding undesired magnetic objects present in said well, said main body provided with a connector to said drill- or coiled tubing string (1, 1b) at its upper end, characterized by - said main body further comprising a generally cylindrical upper housing with a central channel with laterally directed curl flow forming nozzles through the cylindrical wall of said upper housing, said nozzles leading out into one or more helical grooves between helical ridges, - said magnet comprising permanent magnets (31, 32, 33, 34, 35) arranged in a magnetization pattern which concentrates their combined magnetic flux through said downwards facing surface, - said upper housing's vertical channel extending near its lower end to peripherally directed channels extending to an outer wall of said lower housing about said magnets (3, 31, 32, 33, 34, 35) and leading to axially directed peripheral nose ports at a peripheral lower end of said lower housing and arranged for flushing fluid ahead of said magnet (3, 31, 32, 33, 34, 35), - said central channel provided with a vertically displaceable cylindrical flow control sleeve which is provided with a closing seat near its lower end so as for receiving a ball for shutting off the flow to said nose ports and redirecting said flow through apertures (84, 84a, 84b, 84c) in the wall of said sleeve to said curl flow forming nozzles. - said main body further comprising a generally cylindrical upper housing with a central channel with laterally directed curl flow forming nozzles through the cylindrical wall of said upper housing, said nozzles leading out into one or more helical grooves between helical ridges, - said magnet comprising permanent magnets (31, 32, 33, 34, 35) arranged in a magnetization pattern which concentrates their combined magnetic flux through said downwards facing surface, - said upper housing's vertical channel extending near its lower end to peripherally directed channels extending to an outer wall of said lower housing about said magnets (3, 31, 32, 33, 34, 35) and leading to axially directed peripheral nose ports at a peripheral lower end of said lower housing and arranged for flushing fluid ahead of said magnet (3, 31, 32, 33, 34, 35), - said central channel provided with a vertically displaceable cylindrical flow control sleeve which is provided with a closing seat near its lower end so as for receiving a ball for shutting off the flow to said nose ports and redirecting said flow through apertures (84, 84a, 84b, 84c) in the wall of said sleeve to said curl flow forming nozzles.