Tunisian opposition politician Mohamed Brahmi has been shot dead outside his home in the capital, Tunis, officials say. Mr Brahmi, 58, led the nationalist Movement of the People party. It is the second time an opposition party leader has been killed this year. Protesters have gathered in Tunis and in Mr Brahmi's hometown, Sidi Bouzid, calling for the government to resign. Tunisia largest labour union has announced a general strike for Friday. In February, prominent secular politician Chokri Belaid was also shot outside his house in Tunis. His murder sparked nationwide mass protests and forced Prime Minister Hamadi Jebali to resign. An uprising in Tunisia in late 2010 kick-started a series of revolutions that spread through the Middle East and became known as the Arab Spring. But there has been deep division between Islamists and secular opponents since the revolution, the BBC's diplomatic correspondent James Robbins reports. Many Tunisians, particularly the young, complain that their quest for secular democracy has been hijacked by intolerant Islamists, including the Muslim Brotherhood which forms part of the current government, our correspondent says. 'Cowardly crime' Gunmen on a motorbike shot Mr Brahmi in his car in front of his wife and daughter on Thursday morning, Movement of the People party officials said. Local media reported the assailants fired 11 bullets at the politician. It is not known yet who was behind the attack. The family of Mr Brahmi has accused the governing Islamist Ennahda party of being behind the killing. The party has not responded to the claim, but released a statement expressing "sadness and shock" at the "cowardly and despicable crime". Mr Brahmi's wife, Mbarka, and her daughter Belkis were joined by angry Tunisians outside the hospital in Tunis where the politician died. Large crowds also gathered in front of the Ministry of Interior in the capital in protest at the killing. There were also reports of demonstrators converging in the city of Sidi Bouzid, the birthplace of the Arab Spring. "People have blocked roads and set tyres alight," a local resident told the Reuters news agency. The killing came as Tunisia celebrated the 56th anniversary of becoming a republic after gaining independence from France. French President Francois Hollande condemned Mr Brahmi's murder and called on Tunisians to unite behind the democratic transition. Human rights organisation Amnesty International said the killing was a "blow to the rule of law in Tunisia", which was experiencing a "worrying tide of political violence". Mr Brahmi founded the Movement of the People party after the 2011 revolution. He was also a member of the National Constituent Assembly, which is drafting a new constitution. The assembly announced Friday would be a day of mourning. Mr Brahmi was not as big a political figure as Mr Belaid, but he too was a leftist critical of Ennahda. Ennahda came to power following the overthrow of long-term ruler Zine al-Abidine Ben Ali in January 201.. The party has faced growing popular unrest over a faltering economy and a rising extremist Islamist movement. After Mr Belaid's assassination in February, many Tunisians accused Ennahda of not doing enough to stamp out a rise in Islamist violence, with some critics saying the party was actively fomenting it, correspondents say. The party denied the accusations.