Tens of thousands of demonstrators have marched in the Tunisian capital, Tunis, calling for the resignation of the Islamist-led government.The rally marked a 40-day mourning period since the killing of opposition MP Mohammed Brahmi in July.His murder, along with the shooting of another prominent leftist politician in February, have sparked mass protests.Talks between the opposition and the ruling Ennahda party have so far failed to achieve a major breakthrough.The moderate Islamist government has blamed Salafist hardliners for the killings of Mr Brahmi and secular opposition leader Chokri Belaid.The opposition coalition, led by the National Salvation Front (NSF), has accused Ennahda of failing to rein in radical Islamists and improve the faltering economy. 'A government for all'Protesters in central Tunis gathered outside the ANC building, where lawmakers were forced last month to suspend the drafting of a new constitution because of the unrest.Chanting anti-Ennahda slogans, demonstrators waved national flags and held up images of Mr Brahmi."We need a government for all Tunisians," one protester told the Reuters news agency.Other large opposition protests have been held in Tunis in recent days.The NSF, which organised Saturday's rally, said it planned more demonstrations in the weeks to come.Meanwhile, Ennahda has also been holding mass rallies throughout August in support of what it calls its "legitimacy to govern".The cabinet of Prime Minister Ali Larayedh has pressed the opposition to accept its roadmap, which envisages legislative and presidential elections by the end of the year.The Ennahda party was elected after the overthrow of President Zine el-Abidine Ben Ali in January 2011.It has been facing unrest since Mr Brahmi, the leader of the small left-wing Popular Movement party, was killed outside his home in Tunis on 25 July.In February, the first Islamist-led government was brought down after Chokri Belaid was shot in the neck and head on his way to work.It was the first time a political leader had been assassinated since Tunisia's Arab Spring uprising.Dozens of opposition members withdrew from the ANC in protest at the killings.