CAIRO (AFP) - Egyptian protesters joined hundreds already camped out in Cairo's Tahrir Square on Sunday ahead of mass nationwide rallies to demand the resignation of Islamist President Mohamed Mursi.

Demonstrators streamed into the square, where tents have been pitched and anti-Mursi banners hung on walls.

In Cairo's Nasr City neighbourhood, Mursi's supporters vowed to pursue a sit-in to defend the legitimacy of the president, who assumed power one year ago after Egypt's first free presidential elections.

Police and troops have deployed to protect key buildings around the country, security officials said. The health ministry said hospitals have been placed on high alert.

The anti-Mursi protests were called by Tamarod, a grassroots movement that says it has collected more than 22 million signatures to a petition calling for early presidential elections.

The figure, which compares with the 13.2 million votes to 12.3 million by which Mursi won election last year, cannot be verified.

The week leading up to Sunday's anniversary saw street violence in which eight people were killed, including an American, and scores more injured, as the two sides held rival demonstrations.

Several newspapers called Sunday "Judgment Day". Others, like the independent daily Al-Tahrir had a clearer message for the president: "Leave," it said in red on its front page.