Tunisian opposition leader Chokri Belaid was shot dead today - the first political assassination in post-revolutionary Tunisia.
Mr Belaid, a lawyer and a leading member in the left-wing Popular Front alliance, was shot as he left his house in the capital Tunis.
Soon afterwards, thousands of people protested in front of the Interior Ministry, blaming the government for Mr Belaid's killing.
In the city of Sousse police fired tear gas at protesters, while in several towns offices of the Islamist Ennahda party were attacked.
Mr Belaid had been a fierce critic of Ennahda, which dominates the coalition government.
Ennahda said it wasn't involved in the killing, which it labelled a "heinous crime" that threatened Tunisia's "security and stability."
Mr Belaid had accused Ennahda of not doing enough to stop violence by conservative Islamists who have attacked theatres and art exhibitions.
He had been particularly outspoken against the so-called Committees to Protect the Revolution that most believe to be behind the violence.
These groups are said to be affiliated with Ennahda and claim their mission is to seek out remnants of the old regime.
Mr Belaid's family said he regularly received death threats, including on Tuesday, but refused to give in and limit his activities.
Over the weekend religious radicals disrupted a rally led by Mr Belaid in northern Tunisia, part of a string of political meetings disrupted by gangs.
President Moncef Marzouki, a member of a secular coalition party, called the assassination a threat against all Tunisians.
"Chokri Belaid was murdered this very day knowing I was going to be speaking to you," he told the European Parliament in Strasbourg today.
"This is a letter being sent to us that we will refuse to open.
"We reject that message and we will continue to unmask the enemies of the revolution."
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