At a hearing before the U.N.’s highest court, South Africa on Tuesday called Israel’s policies toward Palestinians an “extreme form of apartheid” and argued that its occupation of territory sought for an eventual Palestinian state was “fundamentally illegal.”

The hearing at the International Court of Justice in The Hague is one of two matters being heard about Israel, part of a concerted effort to leverage the authority of the court and the global reach of the U.N. to stop the war in Gaza and examine the legality of Israel’s policies toward the Palestinians.

Starting this week and lasting six days, the court is hearing arguments on Israel’s conduct, following a request by the United Nations General Assembly more than a year ago. In the other matter, a case, which began in January, South Africa accuses Israel of committing genocide in its ongoing war against Hamas in Gaza.

Israel has strongly rejected those accusations.

The latest proceedings, which began on Monday, focus on the legality of Israel’s “occupation, settlement and annexation” of Palestinian-majority territories, including the West Bank and East Jerusalem. South Africa and many other countries that have asked to address the court argue that Israel’s decades-long occupation violates the Palestinians’ right to self-determination and that its security apparatus, including a wall, amounts to racial segregation.

More than 50 countries and three regional blocs are scheduled to argue before the 15-judge bench over the next week, a level of participation never before seen at the court.

The hearings on Israel’s policies have gained urgency amid the bloodshed of the war in Gaza. They come less than a month after the court ordered Israel to restrain its attacks in the Hamas-controlled territory in the genocide case.