(Tunis) – The victims of the deadly attack in Tunis on November 24, 2015, deserve a speedy, transparent, and effective investigation into the attack. The attack on a bus killed 12 presidential guards and wounded 20 others, including four civilians, according to the authorities.

“The victims of this crime, including their families, have a right to know what happened and who was responsible,” said Amna Guellali, Tunisia office director. “Tunisian authorities should ensure that those responsible are brought to justice.”

The extremist group Islamic State, also known as ISIS, has claimed responsibility for the attack. President Beji Caid Essebsi declared a 30-day state of emergency and a nighttime curfew.

Authorities have not yet provided a full account of the attack. News reports said that just after 5 p.m. an explosion hit a bus carrying members of the presidential guard waiting to start their daily shift on the Mohamed V avenue, a major street close to the Interior Ministry.

Armed extremist groups have targeted Tunisian security forces in numerous attacks since 2011, killing a total of more than 60 police and army agents. On March 18, two gunmen attacked the Bardo Museum, adjacent to parliament, killing 21 foreign tourists and one Tunisian security officer. On June 26, a gunman went on a shooting rampage at a beach resort in Sousse, killing 38 tourists.

In early November, Jund al-Khilafa, a group affiliated with ISIS, claimed responsibility for the murder of a 16-year-old shepherd, Mabrouk Soltani, in the Jebel Mghila Mountains, near Sidi Bouzid, the birthplace of Tunisia’s uprising. A video posted by the group claimed the teenager was an army informer.

Essebsi had declared a state of emergency in June following the Sousse attack, lifting it in October. Under a 1978 presidential decree, the president may declare a state of emergency of up to 30 days, renewable, in response to serious disturbances.

The decree gives the executive – in practice the Interior Ministry or local governor – the authority to prohibit strikes and demonstrations deemed to threaten public order, order the house arrest of anyone whose “activities are deemed to endanger security and public order,” and prohibit gatherings “likely to provoke or sustain disorder.” The executive also can “take any measure to ensure control of” the press and other publications of any nature, as well as radio, television, film screenings, and theater performances.

Article 80 of the 2014 Tunisian constitution gives the president the authority to decree exceptional measures “in the event of imminent danger that threatens the nation or the security or independence of the country and that hampers the normal operations of state institutions.” The article calls for a return to the normal functioning of state institutions and services at the “earliest opportunity.” The constitution gives the president of the parliament or 30 of its members the right to petition the constitutional court to rule on whether the conditions justify a state of emergency. However, parliament has not yet established the constitutional court.

Under international law, countries may limit some rights during public emergencies that threaten the life of the nation. But they can only restrict rights to the extent that is strictly necessary for the situation, and some rights, including that of judicial review of detention, can never be removed.

“Yesterday’s killings highlight the Tunisian authorities’ duty to protect the right to life in Tunisia,” Guellali said. “But now more than ever, Tunisian authorities have a responsibility to stay committed to a rights-respecting society and democratic principles.”