Tunisian security on Sunday raided the home of the Dignity Coalition member MP Abdellatif Alaoui and arrested him on charges of 'plotting against state security'.
In a post on Facebook, Alaoui wrote: "A squad from Al-Gorjani [a security centre] is raiding my house and arresting me now."
Ennahda, which has the largest parliamentary bloc with 53 deputies, said a security squad raided Alaoui's house and that of journalist Amer Ayad, arresting them both, intimidated their families and held them pending a military investigation.
Ennahda stressed that it rejects the authorities' moves "to try civilians before military courts, as it violates their right to a fair trial."
It stressed "the need to respect the independence of the judiciary." And warned against "attempting to bypass this democratic gain by presenting detainees to the military judiciary." This, the party added, "reminds Tunisians of the era of tyranny and injustice."
The movement expressed its "fear that the arrest of MP Abdellatif Alaoui came with the aim of preventing a quorum for the meeting of the office of the Assembly of the Representatives of the People [the highest body in parliament], and further attacking the parliament and its legislative and oversight role defined by the constitution."
The body includes 13 members, including the speaker and his two deputies, and its meetings are only valid if two-thirds of its members are present. The Speaker of Parliament is Rached Ghannouchi, head of the Ennahda movement.
On Friday, Parliament announced in a statement the start of its new parliamentary session, and rejected the measures taken by the country's President, Kais Saied, blaming him for the closure of the legislative institution, and the consequent disruption of its vital interests.
Saied has held nearly total power since 25 July when he sacked the prime minister, suspended parliament and assumed executive authority citing a national emergency.
The majority of the country's political parties slammed the move as a "coup against the constitution" and the achievements of the 2011 revolution.