United Nations officials warned that Lebanon was staring down a “catastrophic” humanitarian crisis as the number of internally displaced people hit 600,000 and Israel pressed its offensive against Hezbollah fighters, AFP reports.

Hezbollah said its fighters were locked in clashes with Israeli troops in southern Lebanon, using rocket-propelled weapons to repel Israeli attempts to breach the border.

“Lebanon finds itself facing a conflict and a humanitarian crisis of catastrophic proportions,” Jeanine Hennis-Plasschaert, the UN Special Coordinator for Lebanon, told a briefing.

She expressed “hope that Israel too will now be ready to add its support to the many calls and appeals that are out there” for de-escalation.

The UN’s humanitarian coordinator for Lebanon Imran Riza said that Lebanon was facing “one of the deadliest periods” in its recent history, reporting that 600,000 people are internally displaced — over 350,000 of whom are children.

“Even wars have rules,” he said.

Israel has refused to rule out strikes on Beirut’s civilian airport and its access roads, even as thousands of people continue to flee the country by air and road every day.

“We are not targeting civilians. But at the same time, if we will find Hezbollah activities or intention to launch rockets into Israel, we will do what any other country would do about it,” said Israel’s ambassador to the UN Danny Danon.