Rocks, teargas, firebombs and gunfire made darkened streets in central Cairo a battle zone as hard-core protesters demanding an immediate end to army rule fought riot police around government buildings close to Tahrir Square.
A heavy police presence in Amiens ensured no repeat of violence in the northern French city overnight, after President Francois Hollande pledged to do all in his power to stamp out unrest.
Northern Ireland's first and deputy first ministers held crisis talks with politicians and leaders of the pro-British Orange Order in a bid to stop the sectarian violence which has engulfed Belfast over the last three days.
Rioting prisoners torched buildings at a low-security British jail, an incident the prison guards' union said highlighted the risks of government plans to slash spending on the justice system.
Police fired tear gas at dozens of youths hurling stones in central Athens and a strike against austerity brought much of Greece to a halt during talks on the next slice of a bailout package.Police said 17 demonstrators and two policemen were hurt in the clashes.
Crowds attacked riot police and set two squad cars alight in north London following a protest at the fatal shooting of a man by armed officers earlier in the week.
Well-armed inmates in one of Venezuela's notoriously overcrowded prisons rioted over the weekend, killing 25 people, the government said.
A jail riot in southwestern Venezuela killed dozens of people on Friday, local media reported, the latest incident in the ongoing crisis in the South American nation's crowded prisons.
A prison riot in southwestern Venezuela killed 61 people, a hospital official said, although the government has refused to give an official death toll in the bloody standoff that highlighted chaos in the country's jails.
Bahrain riot police fired tear gas and stun grenades at anti-government activists and members of the Force India race team were caught up in a petrol bomb incident as unrest simmered ahead of this weekend's Formula One Grand Prix.