One week into the ceasefire, a new kind of violence is plaguing the Gaza Strip. Public executions, arson attacks and gun battles have raised the spectre of a slide into civil chaos as Hamas battles armed groups it accuses of collaborating with Israel. Experts say Hamas is attempting to reassert its authority following Israel's withdrawal from parts of the Gaza Strip. But members of three anti-Hamas militias, operating from areas still controlled by Israel, have told Sky News they have no