At least six people were killed on Friday in clashes across Egypt as police dispersed thousands of protesters demanding deposed Muslim Brotherhood president Mohammad Mursi be reinstated.

At least six people were killed on Friday in clashes across Egypt as police dispersed thousands of protesters demanding deposed Muslim Brotherhood president Mohammad Mursi be reinstated, officials said.

Three people were killed in Cairo, and three others in the cities of Ismailiya, Fayoum and Alexandria, as the protesters fought with police and civilian opponents, said the health ministry.

At least 42 people were wounded in the violence, and the interior ministry said 122 protesters were arrested.

Protesters in the capital torched a police vehicle using petrol bombs, a security official said. State media said residents extinguished the fires.

In the upscale neighborhood of Maadi, police fired tear gas near a military hospital as protesters threw fireworks at them.

In an eastern neighbourhood of Cairo, police also used tear gas against thousands of Morsi supporters who burnt tires and threw fireworks at security forces. Gunshots were also heard.

Cairo's main squares were sealed off by security forces using barbed wire and military vehicles.

They included Tahrir Square, as well as Rabaa al-Adawiya and Nahda squares, which were the sites of a bloody crackdown on Mursi's supporters in August.

Since the president's ouster, his supporters have staged near-daily protests calling for his reinstatement, particularly after Friday prayers.

Friday's protests come as a pro-Mursi Islamist coalition spearheading the protest movement called for demonstrations ahead of the resumption of his trial on Wednesday.

Mursi is being tried on charges of inciting the killings of protesters during his presidency. He will also stand trial on January 28 over a jailbreak during the 2011 popular uprising that toppled long-time ruler Hosni Mubarak. A date for him to be tried on espionage charges has yet to be fixed.