Tunisian security forces engaged in a gunbattle overnight on Saturday as they arrested a suspect in last July's murder of opposition politician Mohamed Brahmi, the interior ministry's spokesman said.
Brahimi was the second of two opposition politicians to have been assassinated last year by suspected jihadists as Islamist violence rocked the North African country, which was the birthplace of the Arab Spring revolutions in 2011.
The security forces "surrounded a house [near the capital, Tunis] where a terrorist group had holed up. Following a sustained exchange of fire, four elements were arrested", interior ministry spokesman Mohamed Ali Aroui said.
"Among them is Hmed el-Melki, alias 'Somali', one of the elements implicated in the assassination of the martyr Mohamed Brahmi," he said.
"The interior ministry stresses that it was a successful operation," the spokesman said without revealing the identities of the other suspects.
The announcement came after the government said last Tuesday that the suspected Islamist assassin of Chokri Belaid - the first of the murdered opposition politicians - had been killed in a police raid.
Gunmen killed Belaid on February 6 last year and Brahmi on July 25, both of them outside their homes.
Authorities blamed the murders on the Ansar al-Sharia, a jihadist outfit accused of links to al-Qaeda.
Belaid was a charismatic leftist politician and virulent critic of the Islamist party Ennahda then in power. His murder triggered massive protests.