Palestinians in northern Gaza have reported fierce air and artillery strikes as Israeli troops backed by tanks pressed into the enclave with a ground assault that prompted more international calls for civilians to be protected, Reuters reports.

Israel’s military said it had struck “over 600 militant targets” over the past few days as it continued to expand ground operations in the Gaza Strip — where Palestinian civilians are in dire need of fuel, food and clean water as the conflict enters its fourth week.

“IDF troops killed dozens of terrorists who barricaded themselves in buildings and tunnels, and attempted to attack the troops,” the military said in a statement.