Massive nationwide protests that Egypt's opposition plans for June 30 are taking on a dangerous edge.

Opponents of Islamist President Mohammed Morsi are convinced that this is the best and perhaps the last opportunity to drive him from power. They say they have tapped into widespread public discontent over shortages, broken infrastructure, high prices and lack of security, and can bring that anger into the streets.

Morsi's Islamist backers have vowed to defend the president with counter-demonstrations. Police have signaled they want to stay out of the conflict. The powerful military, widely suspected to be at odds with the president, is keeping its cards close to its chest.

As a result, fears are high of potential violence on the day, the anniversary of Morsi's 2012 inauguration as Egypt's first freely elected leader.

The date is shaping up as the culmination of polarization that has sharpened throughout the year. Protests erupted repeatedly the past year — frequently leading to clashes with Islamist supporters of Morsi — but often they were fueled by particular issues like political maneuvers by Morsi or police brutality.

This time, Morsi's opponents, led by a mix of liberal and secular movements and street activists, say the sole purpose is to force him out by showing the extent of public rejection of his presidency. Many talk as if that is a matter of "when" and not "if." They plan ambitious "post-Morsi" steps: suspending the Islamist-backed constitution and naming the chief justice of the Supreme Constitutional Court as interim president, followed by the drafting a new constitution by a panel of experts and new presidential elections.

"We will take to the streets and the squares and stage sit-ins," said Hossam Mustafa, the chief organizer for the protests in southern Egypt. "We will not leave until the president leaves. We will win back Egypt for all Egyptians."

Already, protest organizers have clashed with Morsi supporters in several parts of the country, including clashes in the Nile Delta city of Tanta on Tuesday that left 10 injured. On Sunday night, clashes in the oasis province of Fayoum southwest of Cairo left at least 100 injured, and similar fights have broken out in the Mediterranean port city of Alexandria and the Nile Delta city of Damanhour.

In expectation of possible violence, the gates of Morsi's Cairo presidential palace have been reinforced. The walls of the headquarters of the Muslim Brotherhood, the Islamic group from which the president hails, have been fortified.

The protest campaign is rooted in an activists' petition drive the past few months called "Tamarod" — or "Rebel" — that claims to have collected up to 15 million signatures on a call for Morsi to step down and for early elections to be held. Organizers of the campaign say its success shows how anger at the government and the Brotherhood has transcended the core opposition to the public at large.

"The will of Egyptians is stronger than anyone," Tamarod spokesman Mahmoud Badr told reporters on Tuesday. "The Egyptians who removed the tyrant Hosni Mubarak will most certainly be able to remove the failed tyrant Mohammed Morsi." He vowed the protest campaign can continue as long as needed, even as summer temperatures rise and the Muslim holy month of fasting, Ramadan, begins, around July 10.

Morsi's supporters, in turn, have depicted the campaign — and the planned protests — as an attempt by supporters of ousted autocrat Hosni Mubarak to overturn democracy. Morsi, whose term is four years, has vowed to deal "decisively" with those trying to force him out.

Senior Brotherhood leader Essam el-Erian told The Associated Press on Monday that the protest calls are "unconstitutional, illegal and irrational" and are not backed by genuine popular support. He cast doubt on the Tamarod signatures, reflecting claims by Morsi supporters that they are forged.

Raising the specter of clashes, el-Erian said Morsi's supporters would defend the presidential palace in Cairo's Heliopolis district if "state institutions" fail to defend it against the protesters.

Some hard-line clerics have issued fatwas, or edicts, saying that organizers and participants in the planned protests are "kuffar," or non-believers, who deserve to be killed.

Assem Abdel-Maged, a senior leader of the hard-line Gamaa Islamiya, said the protest organizers are communist and "radical' Coptic Christians. "It is another phase of the counter-revolution that we have suffered from for so long," he said.

Hanging over the June 30 plans is the sense of a year's building tension coming to a head, centered on the question of the basic legitimacy of the troubled political system that emerged after Mubarak's fall in February 2011. In the polarization, talk of national reconciliation is falling on deaf ears.

Morsi opponents accuse him and the Muslim Brotherhood of using their victories in a string of post-Mubarak elections to monopolize power. June 30 is crucial, the campaigners argue, because the Islamists are increasing their hold and it will eventually become difficult to remove them.

For Morsi's supporters, the protest campaigners are trying to overturn democracy itself because they are unable to compete at the election box. They say old regime loyalists have frustrated Morsi's attempts to deal with the nation's woes, which they argue are worsened by repeated opposition protests.

In last year's election, Morsi defeated Mubarak's last prime minister Ahmed Shafiq in a runoff, with about 52 percent of the vote. His win is widely thought to have been possible only because of the support of young reform activists who did not want a Mubarak loyalist to rule. The same activists are now at the forefront of the opposition.

They say the Brotherhood and its Islamist allies have run roughshod over the judiciary, stacked the deck by pushing through a constitution they largely wrote, imposed their agenda and broke campaign promises for an inclusive administration, freedom of expression and consensus.

The anti-Morsi campaign has been fueled by widespread frustration over host of troubles in the nation of 90 million people, from surging crime, rising prices and unemployment to power cuts, fuel shortages and traffic congestion. Many of those signing the Tamarod petition have blamed Morsi for failing to deal with the problems.

"It is a surrealistic and absurd regime that will not and cannot be allowed to continue," said reform leader and Nobel Peace Laureate Mohamed ElBaradei. "We must put an end to it with our own hands and through peaceful and civilized means."

Islamist parties loyal to Morsi plan protests of their own across the nation Friday and are considering occupying sites where the president's opponents plan sit-ins on June 30.

Mustafa, the anti-Morsi organizer in the south, said he fully expects violence on the protest day in his home province of Assiut, as well as in Minya province to the north. The two provinces are Islamist strongholds and have large communities of Christians opposed to Morsi's government.

A police officers association announced over the weekend they would stay on the sidelines on June 30, protecting only their own installations and key facilities like banks, foreign embassies and hospitals.

"We promised ourselves not to repeat past mistakes. The police are the police of the people and the state," they said in a statement. "We hereby pledge not to use a baton or a firearm against any peaceful protester and that we abide by complete neutrality."

The Interior Ministry, in charge of the police, says security forces will monitor protests from a distance and intervene only in the event of clashes.

The military's position is less clear. Its top brass have over the months sent subtle but telling hints of their displeasure over the policies of Morsi and his Islamist backers. They, however, have also seized every available opportunity to make clear that their mandate is not just to protect the nation against external threats but also to maintain security at home and that they will side with the people if they ever intervene.