Israel’s military said it opened fire on Tuesday to remove a threat posed by suspects who approached its forces in the northern Gaza Strip, and health authorities in the enclave said at least six Palestinians had been killed by Israeli fire.

The military said the suspects had crossed a boundary for an initial Israeli pullback under a U.S.-brokered ceasefire plan, in a violation of the deal.

Gaza’s local health authority said the Israeli military killed six Palestinians in two separate incidents across the enclave on Tuesday.