Israel's military is starting the next phase of its war against Hamas, targeting the Islamist group's labyrinth of tunnels and command structures in northern Gaza in an operation that may take months to complete, security sources said.

Israeli forces have pounded Gaza from the air and used ground troops to divide the coastal enclave into two, in an offensive launched after Hamas gunmen killed 1,400 people and took some 240 hostages in a cross-border attack on Oct. 7. In recent days, Israeli troops have surrounded Gaza City and battled Hamas fighters as they pushed deeper into its streets.

With casualties in Gaza topping 10,000, according to Palestinian health officials, Israel has come under mounting diplomatic pressure for a humanitarian cease-fire.