Members of Tunisia's main ruling Islamist party called for a rally in the capital on Saturday, a day after police clashed with protesters at the funeral of murdered opposition figure Chokri Belaid.
The shooting of Belaid, a leftist leader and outspoken government critic by a lone, hooded gunman on Wednesday plunged Tunisia into new post-revolt turmoil as tension and division within the Ennahda party itself intensified.
Armoured vehicles and troops were stationed along Habib Bourguiba Avenue, the epicentre of the 2011 revolution that toppled autocratic president Zine El Abidine Ben Ali and sparked a wave of Arab world uprisings.
The Ennahda demonstration was to take place on the landmark boulevard on Saturday, the party said in a statement.
The protest would "defend the legitimacy of the national constituent assembly," where the Ennahda-dominated coalition holds a majority, and would "fight against (the political) violence" it said the opposition is using.
Tens of thousands of protesters took to the streets on Friday for the funeral of Belaid, and clashes with police, who fired tear gas, led to 132 arrests, the interior ministry said.
The opposition blames Ennahda for Belaid's murder, but the ruling party vehemently denies any involvement.
"With our blood and our souls we will sacrifice ourselves for the martyr," shouted mourners on Friday, who also chanted slogans denouncing the ruling Ennahda party as "assassins".
Belaid, 48, was shot dead as he left home for work on Wednesday.
The murdered politician's eight-year-old daughter fainted amid chaotic and emotional scenes as Friday's procession began its three-and-a-half kilometre (two-mile) journey to the cemetery.
"My son is a man who lived with courage and dignity. He was never afraid, he left as a martyr for our country," said Salah Belaid, his father.
"We lost a great hero," Beji Caid Essebsi, a former premier and now a centre-right opposition leader, told AFP.
As a general strike called by the powerful 500,000-strong General Union of Tunisian Workers (UGTT) took hold, troops were deployed in the towns of Zarzis in the south and Sidi Bouzid, birthplace of the 2011 uprising.
The strike was believed to be the biggest since January 14, 2011 -- the day Ben Ali fled to Saudi Arabia, where he remains in exile.
The opposition has accused Ennahda of eliminating Belaid after months of simmering tensions between liberals and Islamists over the future direction of the once proudly secular Muslim nation.
Tension and division reign within Ennahda itself, after the recent sacking of the party's leader and as Prime Minister Hamadi Jebali attempts to form a new government of technocrats.
But a faction of Jebali's Ennahda party rejected the move, fuelling uncertainty as political infighting delays a deal on a new constitution.
The Tunisian premier insisted late on Friday that he was committed to his planned reshuffle.
"I stick by my decision to form a government of technocrats and I would not need the support of the constituent assembly," Jebali was quoted as saying by the TAP news agency.
Four opposition groups including the Popular Front said they were pulling out of the National Constituent Assembly, elected in October 2011 but which has failed to draft a new constitution.
The Tunisian League for Defence of Human Rights said threats and intimidation were continuing under the Ennahda-dominated government, and called for politicians to be protected.