Cairo, Egypt (CNN) Calls for President Abdel Fattah el-Sisi to step down over corruption allegations moved from social media to the street on Friday night, marking some of the first demonstrations Egypt has seen since Sisi came to power in a military takeover six years ago.

Protesters, many of them young people, rallied in the capital Cairo, as well as several smaller Egyptian cities, chanting, "Sisi get out."

Sisi, who ousted the country's first democratically elected president in a 2013 coup, has shown zero tolerance for protest during his rule . Those who challenge his ban on unauthorized demonstrations are sentenced to lengthy prison sentences and face harsh punishments.

But Egyptians were spurred to the streets after calls on social media from Mohamed Ali, a former building contractor who worked with the country's military.. Ali has posted a series of videos on Facebook accusing Sisi and other officials of misusing public funds.

Sisi has dismissed the allegations as "lies and slanders."

On Friday evening, hundreds of anti-regime protesters gathered in Cairo, near Tahrir Square -- the epicenter of the 2011 Egyptian Revolution -- demanding Sisi's resignation.

Police fired teargas to disperse the protesters, but the demonstrations raged on until the early hours of Saturday morning. Security forces could be seen using riot vans to chase demonstrators down a main thoroughfare in the capital.

"By just saying to Sisi in the street 'get out' in a crowd chanting, we are in front of a pivotal moment in the face of the rule of the military gang," Amr Bakly, an Egyptian blogger and political activist, said of the protests in a post on Twitter.

Footage circulating on social media captured similar demonstrations in Alexandria, Suez, Mahalla, Damietta and Mansoura.

One video showed crowds trampling a large banner of Sisi in Damietta.

In Alexandria, a sea of protesters chanted: "The people want the downfall of the regime." Demonstrators also chanted slogans used in the uprisings against former presidents Hosni Mubarak in 2011 and Mohamed Morsy in 2013: "Leave means go, don't you understand" and "We will not go he must go."

In other unverified footage, security personnel in plainclothes were seen attempting to arrest protesters and pursue others who were filming the rallies.

Mohamed Ali said in a tweet that a protester was killed in Alexandria, but CNN could not verify his claim.

Mohamed Azab, a lawyer at the Egyptian Center for Economic and Social Rights, said his center had documented at least 120 cases of people who had been arrested in Cairo, Alexandria, Damanhour, Damietta, Mahallah and Mansoura.

He confirmed that they didn't receive any reports of casualties by live or rubber bullets.

"There were rumors about people were killed yesterday, which is not true. The police didn't use lethal force." he said.

Ali, who lives in Spain in self-imposed exile, has alleged in videos that have gone viral that Sisi and his generals wasted billions of Egyptian pounds (millions of US dollars) in public funds on villas, luxury hotels and a seaside palace.

Against the backdrop of crippling economic austerity measures and soaring poverty in the country, those allegations have struck a chord. One in three Egyptians now live below the poverty line, according to figures released in July by Egypt's statistics agency.

Riding a wave of support on social media, Ali kick-started a campaign calling for Sisi to step down. His hashtag, #Enough_el-Sisi in Arabic, has trended globally.

In one recent video, Ali called on Egypt's defense minister, Mohamed Zaki, to intervene and arrest the president.