At least 1.4 million Palestinians are currently in Rafah, many of whom fled there from Israeli shelling from other parts of the Gaza Strip.
"Forcing civilians to evacuate Rafah to unsafe zones is intolerable. Israel is bound by international law to provide safety to civilians. We continue to urge Israel not to go ahead with a ground operation in Rafah," Borrell said on his social media.
He also called on Israel to refrain from going ahead with a military operation in Rafah as "this would further exacerbate an already dire humanitarian crisis."
In the night from Monday to Tuesday, the Israeli army started a military operation in the eastern parts of Rafah and took control of the Gaza side of the Rafah crossing with Egypt. Israeli authorities say the operation is aimed at eliminating the remaining battalions of Palestinian movement Hamas in the Gaza Strip. On Friday, Israeli media reported that Israel's military cabinet had approved expanding the ground operation in Rafah.