At least 37 Palestinians have been killed and 1,300 wounded by Israeli troops in clashes on the Gaza border, Palestinian officials say.
The violence comes ahead of the opening of the US embassy in Jerusalem, which has infuriated Palestinians.
They see it as clear US backing for Israeli rule over the whole city, whose eastern part Palestinians lay claim to.
Top US officials, including President Donald Trump's daughter and her husband, are attending Monday's event.
The dedication ceremony is now under way.
Gaza's Islamist rulers, Hamas, have led mass protests in a "Great March of Return" for the past six weeks. Israel says demonstrators are trying to breach the border fence.
Children were among those killed on Monday, the Hamas-run health ministry says.
Palestinians hurled stones and firebombs, while the Israeli military used snipers as black smoke poured from burning tyres.
Israel's army said 35,000 Palestinians were taking part in "violent riots" along the security fence and that its troops were operating "in accordance with standard procedures".