Anti-government protesters have flooded the streets across Egypt, calling for the resignation of President Mohamed Morsi.

Mass rallies on Sunday come a year after Morsi was elected as Egypt's president following the 2011 revolution that toppled the Western-backed regime of Hosni Mubarak.

“The people want the ouster of the regime,” the protesters chanted in the capital Cairo's iconic Liberation Square.

The demonstrators are angry at Morsi's handling of the economy and failure to fulfill his electoral promises. The organizers of the major demonstration for Sunday claim that more than 22 million people have signed petition for the resignation of the president and a snap election.

Anti-government protests were also staged in the coastal city of Alexandria, the Nile Delta cities of Mansura, Menuf, Tanta and Mahalla, the canal cities of Suez and Port Said as well as Zagazig.

Meanwhile, pro-Morsi demonstrators have held rival rallies in support of the president as they say he needs time to implement the changes demanded by the Egyptians.

“… We support President Mohamed Morsi. We would like to tell him not to be affected by the opponents’ protests and not to give up his rights. We are here to support and protect him,” said one of the Egyptian president’s supporters.

At least four people have been killed in clashes in the cities of Assiut and Beni Suef. Many others were also injured.

Reports say clashes broke out between supporters and opponents of Morsi after protesters marched to the office of the Freedom and Justice Party (FJP), the political arm of the Muslim Brotherhood.

Dozens also attacked the Brotherhood headquarters in Cairo with petrol bombs, birdshot and stones, according to Gehad al-Haddad, a spokesman for the movement.

Two people have been reportedly killed and 35 others injured in clashes outside the Muslim Brotherhood’s headquarters in Cairo.

    “It is the biggest protest in Egypt's history,” a military source told AFP on condition of anonymity, noting that “millions” of people have packed the streets across Egypt.

Morsi's spokesman Ehab Fahmy has highlighted the need for a national dialogue in the country, saying, “Dialogue is the only way through which we can reach an understanding... The presidency is open to a real and serious national dialogue.”

However, the opposition has urged the demonstrators to hold their ground until Morsi resigns.

Hundreds of Egyptians have also staged anti-Morsi demonstrations in other countries including the UK and Australia.