The health ministry said two persons were killed in Minya in southern Egypt, a third in Cairo, one in Giza and one woman was killed in Alexandria. At least 15 people were injured in clashes as police dispersed anti-government protests.
Police used teargas and birdshot to scatter supporters of ousted Islamist president Mohamed Morsi and other anti-government activists.
An explosion followed by heavy gunfire was heard near a police base in the canal city of Suez, officials said. The cause of the blast and gunfire was , however, not immediately clear.
The fresh attack, that raised fears of further violence, came a day after four blasts, including a suicide bombing at the police headquarters. Yesterday's blasts killed six persons and wounded nearly 100.
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An al-Qaeda-inspired militant group Ansar Beit al-Maqdis (Champions of Jerusalem) claimed responsibility for yesterday's attacks.
Security sources said 291 Muslim Brotherhood supporters were arrested in Cairo, state-run MENA news agency reported.
Thousands of supporters of the interim military-backed government also gathered to celebrate the anniversary of the revolution in Tahrir and other squares around the country.
There were further reports of clashes in Mohandiseen at an anti-government protest as security forces dispersed people coming out of a mosque.
Ahead of commemorations, security forces had blocked areas of the capital, including Tahrir Square, the epicentre of the popular revolt that toppled Mubarak in 2011.