TUNIS: Castigating Tunisia's Islamist-led government for failing to prevent her husband's assassination, Basma Belaid has captured public attention as a powerful opposition voice in her own right.

She has campaigned to bring down the government since an unidentified gunman shot dead leftist politician Chokri Belaid outside his home last Wednesday, and has led protests this week outside the National Constituent Assembly in Tunis.

Even as she ululated in grief at her husband's funeral, which drew tens of thousands to the streets of the capital on Friday, the silver-haired lawyer flashed defiant victory signs to show she would carry on his political struggle.

"Chokri's assassination should spark a new revolution in Tunisia and my victory sign challenges the government, which should leave immediately," she told Reuters in an interview.

"Today there is a great fear of other assassinations in Tunisia," she said. "But the hundreds of thousands who turned out for the funeral of thanks sent a strong message that there is still great hope in the new Tunisia."

Hours after Belaid was killed, Prime Minister Hamadi Jebali promised to form a technocrat government to take Tunisia to elections, but his plan has run into opposition from his own Islamist Ennahda party, whose leader said on Tuesday he wanted political parties represented in any new cabinet.

No one has claimed responsibility for Belaid's killing, which outraged public opinion and created a political crisis in Tunisia, the cradle of Arab revolts that began two years ago.

Basma Belaid, 48, who also uses her maiden name Khalfaoui, is a lawyer and women's rights activist who has been involved in left-wing politics since her university days.

"My response to Chokri's killers would be argument and democracy, not violence" she said. "I will continue the journey Chokri began to defend our freedoms in a moderate society."

Her husband, who belonged to a small leftist party, was a fierce critic of the dominant Islamist Ennnahda party, expressing the fears of many Tunisians that hard-won freedoms are at risk from religious radicals in the government.

Ennahda has denied accusations from some members of Belaid's family that it was responsible for his killing.

Basma Belaid, who has two daughters aged eight and four, has asked the government to provide protection for her family.

"The biggest threat to Tunisia is violence and militancy and attempts to silence the free voices critical of the country's new rulers," she said, referring to Ennahda.