British police have arrested the UK head of Greenpeace, alongside five other activists, after they poured 300 liters of blood-red dye into a pond at the U.S. embassy on Thursday in protest against the U.S. sale of arms to Israel. Will McCallum, the environmental campaign group's UK head, and the others, disguised as delivery riders on bicycles with trailers, Greenpeace said, tipped the dye into the high-security embassy's semi-circular pond. McCallum and the others were arrested on suspicion of conspiracy to cause criminal damage, which carries a maximum sentence of 10 years in prison. The Met Police did not immediately respond to a request for comment. Areeba Hamid, co-executive director at Greenpeace, said that the dye was biodegradable and designed to wash away naturally. "We took this action because U.S. weapons continue to fuel an indiscriminate war that's seen bombs dropped on schools and hospitals, entire neighbourhoods blasted to rubble, and tens of thousands of Palestinian lives obliterated," she said in a statement.