The suspected Islamist assassin of Tunisian opposition leader Chokri Belaid, whose death last February sparked social and political upheaval, has been killed in a police raid, the government said Tuesday.

Belaid was a charismatic leftist politician and virulent critic of the Islamist party Ennahda then in power. His murder triggered massive anti-government protests and a crisis from which Tunisia has only recently started to emerge.

The assassination of prominent Tunisian opposition figure Chokri Belaid a year ago Thursday ignited a crisis which is only now starting to ease following the adoption of a new constitution.

On February 6, 2013, Tunisians were stunned to learn of the death of the 48-year-old lawyer and leftist politician who had been a fierce critic of Ennahda, the Islamist party that rose to power after the first Arab Spring uprising toppled a long-ruling dictator.

A firefight between security forces and suspected Islamists holed up in a building in the Tunisian capital left a policeman and seven militants dead, the interior ministry said on Tuesday.

"Seven terrorists died. A member of the National Guard was killed and another wounded," a ministry source told Agence France Presse.

U.S. Secretary of State John Kerry Wednesday urged Tunisia's new government of independents to organize elections swiftly as the next step in the country's democratic transition.

The new leadership, which replaces the Islamist-led administration, took the oath of office Wednesday and is tasked with steering the country towards democracy.

Tunisia's new technocratic government headed by Prime Minister Mehdi Jomaa was sworn in Wednesday, replacing an Islamist-led administration under an accord to end political turmoil and prepare for fresh elections.

The formal transfer of power took place at the presidential palace after a marathon overnight parliamentary session in which 149 of the country's 193 lawmakers finally approved Jomaa's line-up.

The lawyer representing 20 Salafists given suspended sentences over an attack on the U.S. embassy in Tunis demanded the "truth" Tuesday about the killing of four assailants, hinting that embassy staff were responsible.

Defense lawyer Monaem Turki branded as "political" the appeals trial of the 20 suspects, which comes after Washington sharply criticized the original sentences for being far too lenient.

Tunisia's leaders on Monday signed the new constitution adopted by lawmakers during the night, a key goal of the revolution three years ago that touched off the Arab Spring.

The historic document, seen as one of the most modern in the Arab world, was signed by outgoing Islamist premier Ali Larayedh, Speaker Mustapha Ben Jaafar, and President Moncef Marzouki during a ceremony at the National Constituent Assembly.

Tunisia's dominant Islamist party expects elections to take place in October, senior Ennahda official Ameur Larayedh told Agence France Presse Monday, the day after parliament approved a new constitution by an overwhelming majority.

"Within six weeks there will be an electoral law. There is a clear path to the next elections, which will probably take place in October 2014," said Larayedh, speaking inside the national assembly.

U.N. Secretary-General Ban Ki-moon welcomed Tunisia's adoption of a new constitution on Sunday, declaring it a "historic milestone" and a model for other countries seeking reform.

Tunisia's transition to democracy "reached another historic milestone with the adoption today of the country's new constitution," Ban said in a statement released by his spokesman Martin Nesirky.

Tunisia's premier-designate Mehdi Jomaa said Sunday he has presented the president with the list of his proposed cabinet of independents, under a roadmap aimed at ending months of political crisis.

"I have submitted the list of members of the proposed government to be subjected to a confidence vote in the National Constituent Assembly," Jomaa announced, saying he hoped it would secure the vote "as quickly as possible."