Clashes have broken out in the Egyptian city of Alexandria between anti- and pro-government supporters that have left at least one dead and more than 80 wounded, according to the state news agency MENA.
The country's interior ministry confirmed on Friday that the man was a US citizen and died from a stab wound to the chest while taking pictures of the clashes.
Some anti-government protesters set fire to the local headquarters of the Muslim Brotherhood's Freedom and Justice Party in the Sidi Gaber area of the city.
Riot police and army helicopters were called in to help stop the violence.
Violence also broke out in other parts of the country with reports of attacks on Muslim Brotherhood offices in several cities and governorates, including Gharbiya, Daqahliyah and Kafr el-Sheikh.
Earlier, several thousand protesters marched along the Alexandria's seafront complaining mainly about economic stagnation.
"There are no services, we can't find diesel or gasoline. We elected [President Mohamed] Morsi, but this is enough," said 42-year-old accountant Mohamed Abdel Latif.
Meanwhile, thousands of supporters and opponents of Morsi were holding rival demonstrations on the streets of the capital, Cairo.
|Live reports from rival rallies in Cairo
Morsi supporters gathered at the Rabia el-Adawiya mosque in Nasr City to assert that "[the government's] legitimacy was a red line", in response to opposition plans for a major rally over the weekend to demand president's resignation.
Thousands of Morsi backers filled the street outside the mosque, chanting religious slogans. "It is for God, not for position or power", they shouted.
"I'm here to defend my voice. If you want Morsi to leave, that's fine, but after four years," said Taher Mohamed, manning a stall and selling pro-Morsi gear at the rally.
Naeem Ghanem, another Morsi supporter accused the opposition of working with the US and Israel.
"Don't believe that everyone is against the president, 90 percent of the people are with Morsi," he said.
Hundreds of opposition protesters have gathered in Tahrir Square, demanding the president's resignation, ahead of a separate major demonstration plannned on Sunday - a year after President Morsi took office.
The opposition activists have been holding a sit-in in the Tahrir Square, the iconic epicentre of the protest movement that ousted former President Hosni Mubarak in 2011, since Tuesday.
Deepening divisions among ruling Islamist and the largely secular opposition have heightened tensions in Egypt.
Don't believe that everyone is against the president, 90 percent of the people are with Morsi
For the past several days, Morsi's opponents and members of his Muslim Brotherhood have been battling it out in the streets of several cities in the Nile Delta in violence that has left at least four dead and more than 400 injured.
Morsi's Muslim Brotherhood group said all the four people who died in Mansura city were its members.
Some people "think they can topple a democratically elected President by killing his support groups," Gehad el-Haddad, a Brotherhood spokesman, wrote on his Twitter account.
Many fear the clashes are a prelude to more widespread and bloodier battles on Sunday.
In a sign of the charged atmosphere, a senior cleric, Sheik Hassan al-Shafie, from Al-Azhar, the country's most eminent Muslim religious institution, warned of the possibility of "civil war" after the street clashes in the Delta.
The opposition accuses Morsi, who is Egypt's first democratically elected president, of failing to fulfill the objectives of the revolution that forced Hosni Mubarak from power in 2011.
They accuse the ruling Islamists of focusing on consolidating power and failing to address Egypt's economic and social problems.
The army, which heeded mass protests in early 2011 to push aside Mubarak, has warned it will intervene again if there is violence and to defend the "will of the people".
Morsi's supporters have vowed that he will complete his four-year term, which ends in 2016.
On Wednesday, Morsi defended his performance in his first year in office. He admitted that mistakes had been made, but offered no concessions for his opponents.