Thousands of anti-government protesters demonstrated Thursday in towns across Tunisia, sparked by the killing a day earlier of six policemen by Islamist militants.

Pro-opposition demonstrators swarmed the northern towns of Kef and Beja, clashing with police and ransacking offices of the ruling Islamist Ennahda party. Thousands more protested in the town of Sidi Bouzid, the birthplace of the 2011 revolution that brought the moderate Islamists to power.

The crowds blame the government of Prime Minister Ali Larayedh for failing to rein in religious extremists, and are demanding that the government resign as earlier promised.

Wednesday's police killings occurred as government envoys and the opposition were about to open long-awaited talks aimed at charting a path to a transitional government and eventual general elections.

The transition process has been at a standstill since the assassination of two secular opposition leaders earlier this year.

On Wednesday, Prime Minister Larayedh told a national television audience that his government still intends to resign, once it has completed negotiations aimed at forming a caretaker government. He spoke after thousands of protesters flooded the streets of Tunis to encourage his departure and that of his government.

The Ennahda party won 2011 elections that followed the ouster of longtime president Zine el-Abidine Ben Ali in a popular uprising earlier that year. But it has since faced mass protests by secular opposition groups that accuse the government of trying to impose an Islamist agenda on one of the Muslim world's most secular countries.