South Africa has called on Israel to release activists on the Global Sumud Flotilla, including Nelson Mandela’s grandson, saying Israel’s interception of the Gaza-bound aid boats was a grave offence and violation of international law, Reuters reports.

“The interception of the Global Sumud Flotilla is another grave offence by Israel (against) global solidarity and sentiment that is aimed at relieving suffering in Gaza and advancing peace in the region,” President Cyril Ramaphosa said in a statement.

Ramaphosa said Israeli forces’ interception of the flotilla in international waters violated an International Court of Justice injunction that humanitarian aid must be allowed to flow unimpeded.

Before leaving South Africa to join the flotilla, Mandela’s grandson Nkosi Zwelivelile “Mandla” Mandela told Reuters that Palestinians’ lives under Israeli occupation were worse than anything Black South Africans experienced under apartheid.