Israeli police say an extremist ultra-Orthodox Jew in prison for a deadly attack on last year's annual Jerusalem gay pride march has plotted another attack on this year's march.

Police spokeswoman Luba Samri says Thursday that police thwarted the plot by Yishai Schlissel and arrested his brother, Michael, as an accomplice.

Schlissel is serving a life sentence for his 2015 stabbing spree. He killed a 16-year-old girl and stabbed seven other people. He had been released from prison weeks earlier after serving a sentence for stabbing several people at the 2005 pride march.

Police would not say how Schlissel plotted an attack from inside prison. Police briefly detained other relatives of Schlissel and ordered them to stay away from the march.

This year's march in Jerusalem will be heavily secured.