Abbas condemns Israeli 'massacres' after Gaza violence

Palestinian president Mahmoud Abbas condemned Israeli "massacres" along the Gaza border after Israeli forces killed 55 Palestinians during clashes and protests Monday coinciding with the opening of the US embassy in Jerusalem.

Abbas, who declared three days of mourning, also said "the US is no longer a mediator in the Middle East," and the new embassy was tantamount to "a new American settler outpost" in Jerusalem.

Hamas, the Islamist movement that runs the Gaza Strip, vowed protests would continue.

"We say clearly today to all the world that the peaceful march of our people lured the enemy into shedding more blood," senior Hamas official Khalil al-Hayya said.

He added that Hamas's armed wing and other militant groups "will not prolong their silence over the crimes of the occupation."

The clashes, which also left hundreds of Palestinians wounded, erupted before a White House delegation and Israeli officials opened the embassy at an inauguration ceremony in Jerusalem and continued throughout the day.

It was the bloodiest day in the Israeli-Palestinian conflict since a 2014 Gaza war.