The Indonesian government warned of “extreme weather and high waves” around the erupting Anak Krakatau volcano on Wednesday, urging people to stay away from a coastline that has already been devastated by a tsunami that killed more than 400 people. Ash spewed from Anak Krakatau, almost obscuring the volcanic island where a crater collapse at high tide on Saturday sent waves up to five-meters high smashing into the coast on the Sunda Strait. The meteorology agency BMKG said late on Tuesday that rough weather around the volcano could make its crater more fragile. “We have developed a monitoring system focused specifically on the volcanic tremors at Anak Krakatau so that we can issue early warnings,” said BMKG head Dwikorita Karnawati. A two-kilometer exclusion zone has been imposed.