Sarah Lynch

Special for USA TODAY

Egyptians gathered in Tahrir Square to mark the 3 year anniversary of the uprising against Mubarak

Brotherhood-led%2C anti-coup alliance called for anti-government demonstrations at more than 30 points citywide

Police said they arrested 139 Brotherhood members in rallies across Cairo on Saturday

CAIRO — Rival rallies kicked off here Saturday on the third anniversary of the nation's uprising, underscoring rigid political divisions since Egypt united against a longtime leader.

In Tahrir Square, the heart of the 18-day uprising against dictator Hosni Mubarak, Egyptians gathered to mark the day with celebrations and to show their support for Egypt's army chief, Gen. Abdel Fattah al-Sisi.

"I'm here today to celebrate the Jan. 25 revolution and to support our military and police against terrorism," said Ashraf Hassan, who came to the square from the Cairo neighborhood Heliopolis. "The Muslim Brotherhood is a terrorist group, and we want them to leave Egypt."

Ahmed Kamel, a health ministry spokesman in Egypt, said 29 people were killed in clashes Saturday between security forces and anti-government protesters nationwide, adding most of those killed were in Cairo. Another 167 people were wounded, he said.

A Brotherhood-led, anti-coup alliance called for anti-government demonstrations at more than 30 meeting points citywide following midday prayers. But it appeared that security forces dispersed most anti-government protests.

"When the police forces came, they attacked us with gas bombs," said Nour Mustapha, a university student who marched in an anti-coup rally Saturday in Nasr City. "The march went another route, and they attacked with live bullets."

Police on Saturday arrested 139 Brotherhood members in rallies across Cairo, the state news agency MENA reported.

"Now the police forces and military don't accept anyone who doesn't want them," Mustapha said. "That's how they think."

Egypt's Muslim Brotherhood has protested for the past six months against the overthrow of Mohammed Morsi last summer.

After Mubarak's 2011 ouster, the Brotherhood was the nation's most popular political force, winning the most seats of any party in a parliamentary vote. Then Morsi, one of the Brotherhood's own, was elected president in 2012 in a major turning point for a movement that was repressed for years under Mubarak.

But the tides dramatically shifted again when millions rose up against Morsi last year in anger over his leadership. Egypt's army chief took charge, a constitution drafted under Morsi was suspended, the nation's Legislature was dissolved, and Morsi was swept into detention. Supporters of the power shift refer to it as the "June 30 Revolution."

Authorities, with seemingly widespread support, now consider the Brotherhood a terrorist group and are intensifying a crackdown on any political opposition.

"The Egyptian authorities are using every resource at their disposal to quash dissent and trample on human rights," Amnesty International said in a scathing report released earlier this week.

"Three years on, the demands of the '25 January Revolution' for dignity and human rights seem further away than ever," said Amnesty's Hassiba Hadj Sahraoui, deputy director of the Middle East and North Africa Program. "Several of its architects are behind bars, and repression and impunity are the order of the day."

But the nation's military and interim leaders are solidly backed by Egyptians who believe Sisi saved the nation from civil war between opposing political groups – and from the Muslim Brotherhood – when he ousted Morsi last summer.

In a sign of the stark political divisions, thousands converged Saturday on Tahrir Square, waving Egyptians flags, honking horns and carrying posters of Sisi.

"The Egyptian army is the strongest in the world, and they never disappointed us – ever," said Ayat Ramadan, 30, dressed in clothing in colors of the Egyptian flag.

Nearby, clashes between anti-government protesters and police erupted.

Egypt's interior minister had urged Egyptians to take to the streets to commemorate the Jan. 25 uprising, which authorities say was protected by last summer's June 30 Revolution.

"The June 30th revolution took place in order to put the Jan. 25th revolution back on the right track after some forces tried to hijack it for personal gain," Egyptian President Adly Mansour said in a speech.

"The revolution came to mend a rift that was caused by the malfeasance of some leaders and individuals who erred from their responsibility to protect this nation and its people," he said. "They abused their power, which was granted to them only to protect and serve the people."

Meanwhile, Ansar Beit al-Maqdis, an al-Qaeda-inspired group, claimed responsibility for a string of deadly attacks that tore through the capital Friday, according to the monitoring service SITE, which tracks international terrorists. The organization, which is based in Egypt's restive Sinai Peninsula, also attempted to assassinate Egypt's interior minister last summer.

The first blast resounded in Egypt's capital Friday around dawn outside a police headquarters in downtown Cairo. Two separate explosions followed almost immediately on the opposite side of the Nile, which runs through the capital, the state news agency MENA reported. A fourth blast took place later in the day in an attack on a police convoy. Six were killed in the blasts and dozens were wounded, the state news agency reported.

In addition, clashes between protesters and security forces Friday killed 14 people, Reuters reported.

Early Saturday, another bomb went off near a Cairo police institution, but caused no casualties, spokesman for the Interior Ministry told the Associated Press.

The U.S. Embassy in Cairo condemned the attacks Friday, and urged Americans to be alert and limit their movements ahead of Saturday's rallies.