TUNIS - Thousands of protesters gathered in Sidi Bouzid, cradle of the Arab Spring uprisings, after a prominent secular opponent of Tunisia's moderate Islamist-led government was shot dead on Wednesday."More than four thousand are protesting now, burning tyres and throwing stones at the police," Mehdi Horchani, a Sidi Bouzid resident, told Reuters. "There is great anger".Thousands were also protesting in Tunis after Shokri Belaid was killed outside his home there on Wednesday.Tunisians rose up against long-time leader Zine al-Abidine Ben Ali after vegetable seller Mohamed Bouazizi set fire to himself in Sidi Bouzid in late 2010.