Egyptian voters have approved a new constitution by 98.1 percent, the elections chief said Saturday, in what the government declared a popular endorsement of the army's overthrow of Islamist president Mohamed Morsi.

The result of the Tuesday-Wednesday vote had never been in doubt, as Morsi's Muslim Brotherhood and other Islamists boycotted it, but the authorities wanted a large turnout in the first democratic test since the ouster in July.

Meanwhile, Morsi will face trial on charges of insulting the judiciary, a judicial source said on Sunday, a signal that Egyptian authorities have no intention of easing a crackdown on the Muslim Brotherhood.

Army chief Abdel Fattah al-Sisi, the general who led the overthrow, had been monitoring the outcome for an indication of support for a possible presidential bid, military officials said.

Electoral commission head Nabil Salib said turnout "reached 38.6 percent" of 53 million registered voters, with only 1.9 percent voting "no."

That turnout proved "that the revolution of June 30 was a popular revolution," a senior government official said at a news conference to announce the results.

It "refuted the doubts of naysayers," said Salah el-Din Abdel Sadeq, head of the government's media arm.

The new charter replaces an Islamist-inspired one adopted in a December 2012 referendum under Morsi with about two-thirds of the vote and a 33 percent turnout.

The United States, a major source of financial aid most of which is military funding, reacted to the news by urging Egyptian authorities to fully implement the rights guaranteed under the constitution.

"It's not one vote that determines a democracy. It's what comes next that will shape Egypt's political, economic and social framework for generations," said US Secretary of State John Kerry.

"As Egypt's transition proceeds, the United States urges the interim Egyptian government to fully implement those rights and freedoms that are guaranteed in the new constitution for the benefit of the Egyptian people, and to take steps toward reconciliation," he said.

The US administration on Thursday said it was closely watching the results of Egypt's referendum, but had not yet decided whether to unfreeze some $1.5 billion in aid.

The military removed Morsi days after millions of protesters began rallying against him on June 30 last year, setting off months of unrest by his followers who decried what they called a "coup."

Presidential and parliamentary elections have been promised for later this year.

AFP - Reuters