TEL AVIV — A humanitarian crisis is unfolding in Gaza after Israel ordered a “full siege” of the territory, causing shortages of electricity, food and water in retribution for Hamas’s deadly attack on Israel on Saturday. The Palestinian Health Ministry in Gaza said health services have reached a “critical stage,” with medicine and fuel expected to run out “imminently” and hospitals at full capacity. U.S. Secretary of State Antony Blinken arrived in Israel on Thursday, telling reporters before his departure that “we want to make sure to the best of our ability — and I know Israel wants to make sure to the best of its ability — that civilians are not harmed.” In recent days, Israel has massed troops near Gaza and called up a record number of 360,000 reservists ahead of an expected ground assault, as Israel Defense Forces continue to target senior Hamas leaders and infrastructure.