An Israeli tank brigade seized control on Tuesday of the Gaza Strip side of the Rafah border crossing with Egypt, authorities said, moving forward with an offensive in the southern city. The Israeli 401st Brigade entered the Rafah crossing early Tuesday morning, the Israeli military said, taking “operational control” of the crucial crossing.

Israel’s seizure and closing of the Rafah crossing in Gaza raises concerns that already scarce supplies will be further depleted and lead to a “catastrophic” disaster. It’s the main route for aid entering the besieged enclave and exit for those able to flee into Egypt.