* Protesters angered by police firing teargas in mosque
* Clashes in capital and provincial cities
* Prime minister accuses protesters of spreading chaos
(Updates with curfew)
By Tarek Amara
TUNIS, July 18 (Reuters) - Tunisia’s prime minister on Monday accused protesters who held a wave of demonstrations over the weekend of plotting to destabilise the country, six months after the revolution that inspired the Arab Spring.
One man was killed at a demonstration on Sunday when soldiers fired into the air to bring the crowd under control.
It was the first reported death in a number of violent protests that have hit Tunis and other cities since Friday.
Prime Minister Beji Caid Sebsi said the protests were intended to spread chaos and derail plans for an election on Oct. 23 that will choose an assembly charged with drawing up a new constitution.
“There is an orchestrated plan to upset the stability of the country,” he said in a televised address.
“Elections will be held as scheduled on Oct. 23 despite everything,” he said. “I appeal to all political parties and citizens to defend the country.”
The Defence Ministry said the demonstrator had been killed in Sidi Bouzid, the town in central Tunisia where a young man killed himself by setting himself on fire last December, providing the spark that set off the Arab Spring revolutions now convulsing much of the region.
“One civilian was killed yesterday evening in Sidi Bouzid when soldiers fired into the air to disperse rioters who had attacked them,” Colonel Marouan Bouguerra told journalists in Tunis on Monday.
The government later said it had ordered an overnight curfew on the town starting on Monday. The curfew would last from 10 p.m. (9 p.m GMT) till 5 a.m. every night until further notice.
The rioting is the starkest sign to date of the friction between Tunisia’s secular establishment and Islamists who have been growing more assertive since the country’s autocratic leader was ousted in a revolution six months ago.
Sunday’s violence was sparked by an incident on Friday when police, trying to break up an anti-government demonstration in the centre of Tunis, fired teargas inside a mosque.
Also on Sunday about 200 youths, many of them with the beards typically worn by Islamists, set fire to a police station in the Intilaka district in the west of Tunis.
In the town of Menzel Bourguiba, about 70 km (45 miles) north of Tunis, four police officers were wounded in clashes with rioters, a police source told Reuters.
Tunisians overthrew autocratic leader Zine al-Abidine Ben Ali in January in a revolution that inspired uprisings in Egypt and elsewhere. (Writing by Giles Elgood; Editing by Jon Hemming)