A state of emergency declared in Ethiopia after the resignation of the country's prime minister will last for six months, the minister of defence has said, as the government seeks to stem political unrest amid long-standing demands for greater freedoms.

The measure, which was first announced by state media after a cabinet meeting on Friday, includes a ban on protests and the dissemination of publications "that could incite and sow discord", Siraj Fegessa told reporters on Saturday.

"The government has previously made several efforts to curtail violence, but lives have continued to be lost, many have been displaced and economic infrastructure has been damaged," Fegessa said, as quoted by Reuters news agency.

The state of emergency order will be sent to Ethiopia's parliament within 15 days for ratification, the minister also said.

It will give law enforcement officers the power to detain anyone suspected of violating "the constitutional order" and the ability to search houses, cars and individuals, all without a court warrant, state broadcaster FANA reported.

Displaying signs "which could stir up violence" is also prohibited, FANA said.

Mass demonstrations

On Thursday, Hailemariam Desalegn abruptly announced he would step down as prime minister and head of the ruling Ethiopian People's Revolutionary Democratic Front (EPRDF) coalition.

He cited ongoing "unrest and a political crisis" in the country as major factors in his resignation, which he described as "vital in the bid to carry out reforms that would lead to sustainable peace and democracy".

Hailemariam, who has sat at the helm of the Ethiopian government since 2012, said he will stay on as prime minister in a caretaker capacity until the EPRDF and the parliament accept his resignation and appoint his successor.

This is the second state of emergency to be declared in Ethiopia in the last two years.

In August 2017, Ethiopia lifted a 10-month state of emergency imposed after hundreds of people were killed in anti-government protests demanding wider political freedoms.

The country's Oromo and Amhara people - who make up about 61 percent of the population - have staged mass demonstrations since 2015 demanding greater political inclusion and an end to human rights abuses.

The protests have continued this month, with many people expressing frustration over a perceived slow government release of political prisoners.

In January, Ethiopia promised to free all political detainees in an effort to "foster national reconciliation". More than 6,000 prisoners have been released so far, news agencies have reported.

On Saturday, the US embassy in Ethiopia said the state of emergency "undermines recent positive steps toward creating a more inclusive political space, including the release of thousands of prisoners".

"Restrictions on the ability of the Ethiopian people to express themselves peacefully sends a message that they are not being heard," the embassy said in a statement.