Israel launched fresh airstrikes in the Gaza Strip on Saturday in response to rocket fire from the enclave and the Palestinian Islamist Hamas group said two of its gunmen were killed in the bombings.

Militants fired at least three rockets toward Israeli towns from the Hamas-controlled strip on Friday, which was declared a "day of rage" by Palestinian factions protesting US President Donald Trump's recognition of Jerusalem as Israel's capital.

"IAF (Israeli Air Force) aircraft targeted four facilities belonging to the Hamas terror organization in the Gaza Strip: Two weapons manufacturing sites, a weapons warehouse, a military compound," the Israeli military said in a statement.

A Hamas source confirmed the two men killed in the strikes belonged to the group which urged Palestinians to keep up confrontation with Israeli forces.

Two more Palestinians were killed in clashes with Israeli troops on the Gaza border on Friday and scores more were wounded there and in the occupied West Bank during the protests.

Across the Arab and Muslim worlds, thousands more protesters took to the streets on the Muslim holy day to express solidarity with the Palestinians and outrage at Trump's reversal of decades of US policy.

Trump's announcement on Wednesday has infuriated the Arab world and upset Western allies. The status of Jerusalem has been one of the biggest obstacles to a peace agreement between Israel and the Palestinians for generations.

Israel considers all of Jerusalem to be its capital. Palestinians want the eastern part of the city as the capital of a future independent state of their own.

Most countries consider East Jerusalem, which Israel annexed after capturing it in the 1967 Middle East War, to be occupied territory. It includes the Old City, home to sites considered holy to Muslims, Jews and Christians alike.

For decades, Washington, like most of the rest of the international community, held back from recognising Jerusalem as Israel's capital, saying its status should be determined as part of the Palestinian-Israeli peace process.

The Trump administration argues that the peace process has become moribund, and outdated policies need to be jettisoned for the sides in the conflict to make progress.

Trump also said he would fulfil his campaign promise and begin the process of moving the US embassy from Tel Aviv to Jerusalem, where no other country has an embassy.