CAIRO, Egypt -- The death toll from the latest clashes between Islamist protesters and security forces in Egypt has risen to 17, a security official said Saturday, less than two weeks ahead of a key referendum on an amended constitution.

Meanwhile, 13 of the country's most prominent human rights groups issued a report condemning the authorities' human rights violations and recent arrests of political activists.

In what were the deadliest street battles in months, Cairo and other heavily populated residential areas on Friday witnessed hundreds of Muslim Brotherhood members and their supporters throw firebombs and rocks at security forces, who responded with water cannons and tear gas.

Health Ministry Spokesman Mohammed Fathallah said 62 people were injured in the violence.

The security official, speaking on condition of anonymity because he was not authorized to talk to the media, said police arrested 258 protesters and confiscated homemade bombs, firearms, knives, fireworks and Molotov cocktails.

Among the security forces, 17 were injured in the clashes, and three vehicles and a traffic office in Egypt's second largest city of Alexandria were set on fire, he said.

The streets were mostly calm on Saturday and Interior Minister Mohammed Ibrahim warned that the police "will not tolerate assaults on the safety of Egypt's citizens."

"The security apparatus will not leave Egypt hostage in the hands of the outlaws," he said during a visit to a security training headquarters.

Street protests have been a regular event across the country since the military ousted Islamist President Mohammed Morsi, who hails from the Brotherhood, in a July 3 coup after millions of anti-Islamist protesters demonstrated to demand his resignation.

Morsi's supporters have taken to the streets to demand his reinstatement and the new military-backed authorities have responded with a crackdown. Hundreds of Brotherhood members were killed when authorities broke up their protest camps, thousands have been arrested and scores were sent to trial.

The government has designated the Brotherhood as a terrorist group and sought to drain its resources, ordering last week the seizure of assets of hundreds of non-governmental groups on suspicions of links to the Brotherhood. Hundreds of the group's leaders and businessmen have also had assets seized.

The Brotherhood has called for a boycott of the Jan. 14 and Jan. 15 referendum on the constitution drafted by a secular-leaning assembly, and plans bigger rallies in the days ahead. A Muslim Brotherhood-led alliance has called on supporters to "continue the days of rage" and to mobilize protesters against the "illegitimate referendum."

The Friday statement had a sectarian tone, accusing a Christian business tycoon and the founder of a liberal party of using militias against Islamists protesters.

Islamists have largely blamed the mass protests that called for Morsi's ouster on the country's Christians, who make up 10 per cent of the population.

Along with the crackdown on the Brotherhood, the military-backed interim government appears determined to silence other secular-leaning activists.

In a joint statement Saturday, 13 of the country's most prominent rights groups documented "violent tactics" used in the arrest and detention of Egyptians -- including activists -- over the past weeks.

"Security forces have returned to violent tactics, arresting activists by breaking into their homes without prior search warrants," said Rami Ghanem, head of the legal department at the organization Arab Mind for Law, Freedoms and Human Rights. "It's very obvious that the detained are being systematically mistreated."

Security forces have cracked down hard on demonstrators breaching the government's recent ban on protests without a permit, which authorities say is needed to bring back peace to the tumultuous streets after three years of political turmoil.

In the latest measures, an Alexandria court sentenced Thursday seven activists to two years in prison on several charges including protesting without a permit and clashing with police last month.

The defendants included two prominent names from Egypt's youth activist movement, Hassan Mustafa and Maheinour al-Masri.

Four of the country's well known activists have been either detained or sentenced for taking part in or inciting illegal protests.

The wife of Alaa Abdel-Fattah, a prominent activist detained for inciting an illegal protest, has said police broke into their home, dragged her husband and beat her before blindfolding and arresting him.

"Courts have joined forces with the prosecution and both swerved from the path of neutrality to become a tool in the hands of political power," the rights groups' statement said.

Militant attacks and suicide bombings have surged in Egypt since Morsi's ouster. While they have been concentrated in the volatile Sinai Peninsula, deadly assaults have also hit the capital and Nile Delta cities. Al-Qaida-inspired group Ansar Beit al-Maqdis has claimed responsibility for most of the attacks.

On Saturday, one roadside bomb killed one soldier and wounded three civilians when it went off next to a military motorcade near the border town of Sheikh Zuweid. A second bomb was found in the same area and dismantled.