CAIRO— A key opposition leader called Saturday for a boycott of upcoming parliamentary elections, saying he will not take part in a "sham democracy."

President Mohammed Morsi's Islamist party, the Muslim Brotherhood, shot back that the opposition was running away from the challenge and wants power without contesting elections.

The exchange reflected a new escalation in political tensions that could spill into even wider strikes and protests ahead of a four-stage vote set to begin on April 28 and last until June. Morsi announced the elections late Thursday night.

"(I) called for parliamentary election boycott in 2010 to expose sham democracy. Today I repeat my call, will not be part of an act of deception," Nobel laureate Mohammed ElBaradei, who leads the main opposition National Salvation Front, wrote on his Twitter account.

He reiterated the opposition's refrain that Morsi, who was elected in a free and fair vote, is acting like former autocratic leader Hosni Mubarak.

Almost immediately after ElBaradei's call, rifts began appearing in the opposition which has struggled to unite since it led the successful uprising two years ago that ousted Mubarak.

Some activists criticized the boycott call, saying it would alienate the masses and allow the Islamists to maintain their domination of parliament.

The Brotherhood has emerged from the uprising as Egypt's most powerful political group, winning both parliamentary and presidential elections.

The deputy head of the Brotherhood's Freedom and Justice Party, Essam el-Erian, responded to ElBaradei's call on his Facebook page saying "running away from a popular test only means that some want to assume executive authority without a democratic mandate."

"We've never yet known them to face any election or serious test," he said of the opposition leaders.

In Egypt's first free elections in 2011, the Brotherhood won nearly half of seats in parliament and the more conservative Salafis won a quarter, making the two Islamist groups dominant.

Liberal and secular parties have trailed significantly in all elections since Mubarak was toppled. Their outreach across Egypt, while growing, is still dwarfed by the Islamists' well organized network of charities and programs that assist the poor.

Nearly half of Egypt's 85 million people live below the poverty line, subsisting on less than $2 per day.

Blogger and commentator Mahmoud Salem, a longtime activist who protested against Mubarak and now opposes Morsi, said he disagreed with boycott calls because it offers no real alternative to the current political impasse.

"Where's ElBaradei's party, its plan, its economic vision? Let's say a boycott is the right answer. What will they do so that they can be competitive in the next election?" Salem said.

He said that ElBaradei is also partly calling for a boycott of the vote because the opposition has been unable to win a significant number of seats.

"In reality, it will end up as a parliament composed of the Muslim Brotherhood, the Salafis, or members of the ex-regime," he said.

The opposition has accused Morsi and his Brotherhood backers of using election wins to monopolize power in tactics similar to the former regime. They accuse him of reneging on a promise to form an inclusive government representative of the Christian minority, women, and liberals.

Elections under Mubarak's three-decade rule were widely rigged and the chamber was dominated by members of his ruling party.

The state-run MENA news agency reported that the president is studying changing the starting of date of elections following an outcry by Coptic Christians in Egypt.

The first phase coincides with Palm Sunday and Easter for Egypt's minority Christians, who tend to travel during the holidays and have consistently voted against the Muslim Brotherhood.

ElBaradei's opposition coalition, which was only formed late last year, had warned for weeks it could boycott parliamentary elections if certain conditions were not met first.

The NSF said it wants a real national dialogue that leads to the formation of a national unity government, changes to the new constitution and stability.

On the second anniversary of the Jan. 25 uprising this year, anger spilled out onto the streets and violence again engulfed the nation.

About 70 people died in a wave of protests, clashes and riots in the past four weeks, and more than half were killed in the city of Suez Canal city of Port Said alone.

The lower house of parliament, which drafts laws in Egypt, was disbanded on June 14, 2012 after the Supreme Constitutional Court ruled that a third of the chamber's members were elected illegally. The upcoming elections are aimed at reinstating the legislature.

Former lawmaker Mostafa al-Naggar, a centrist who beat an ultraconservative, popular Salafi candidate in 2011, said calls for a boycott will be ineffective unless there is unity among the opposition. He said mixed messages will confuse voters and push people away.

He wrote on Twitter that "the decision to boycott the next elections is extremely dangerous because it will clear the arena for the ruling party and its allies to dominate the legislative and executive authorities."

Morsi's supporters say that delaying elections, protesting and boycotting after years of autocracy under Mubarak is affecting Egypt's ability to lure foreign investors and tourists again.

The political unrest has hit Egypt's foreign currency reserves, which have fallen below a critical level to less than $14 billion.

Meanwhile, many residents of the city of Port Said blame Morsi's policies for the turmoil.

A civil disobedience campaign in the city started a week ago.

More than 1,000 people, including hundreds of employees of the Suez Canal Authority, protested Saturday outside one of the vital waterway administration's gates. Shipping in the international waterway has not been affected.

The protesters are demanding retribution for those killed during unrest in the city and for officials to be on trial. On Friday, around 15,000 protested against Morsi and hung effigies of him in the main square there.

There have also been near daily protests in Cairo and in the textile producing city of Mahalla.

Since Morsi's election win as Egypt's first civilian and Islamist president last summer, his popularity has eroded.

Thousands took to the streets in December when he issued power-grabbing decrees temporarily that allowed his supporters to rush a draft constitution to a nationwide vote before a high court packed with Mubarak appointees could disband the process.

It passed with 64 percent amid low turnout and a boycott by thousands of overseeing judges. (AP)