A journalist in Russia's restive Dagestan region was killed in a shooting Tuesday that investigators have linked to his professional work.

Akhmednabi Akhmednabiyev, a journalist with Novoye Delo newspaper known for being critical of authorities, was struck by "many shots" fired by an unidentified gunman early Tuesday. He died on the spot near his home in Makhachkala, the republic's main city, Russia's Investigative Committee said in a statement.

It added that it suspects Akmednabiyev's work was the motive for the attack.

Akhmednabiyev, 53, was the deputy editor of his newspaper and covered political issues, according to the weekly's website. His most recent articles focused on the reasons behind nearly daily attacks in the region.

He also wrote for the popular independent news website Kavkaz Uzel, which covers the North Caucasus and publishes toll figures for the regional unrest that has pitted Islamists against security forces.

According to Kavkaz Uzel, Akhmednabiyev was listed among rights campaigners and journalists deemed supporters of the insurgency in flyers distributed in Makhachkala in 2009. The fliers, which were not signed, promised to kill those on the list in revenge for police officers slain by the militants.

Another name on that list was Gadzhimurad Kamalov, editor of independent Chernovik newspaper, who was killed in 2011.

His murder remains unsolved despite calls by the UN human rights agency and media watchdog groups to push ahead with the investigation.

Akhmednabiyev survived an attempt on his life in January and had received several threats.

The rights group Memorial, which tracks violations in the region, called Akhmednabiyev "one of the few journalists in Dagestan who wrote about the extremes of counter-terrorist operations, about persecution of religious groups, about massive rights violations, about the crimes of the security services."

"It seems that somebody is trying to completely shut down the trickle of truthful information" from Dagestan, Memorial said in a statement.

Attacks on journalists are frequent in Dagestan, Russia's most violent region because of a simmering Islamist insurgency with near daily attacks. In the latest high-profile murder, a young news anchor was shot dead in Makhachkala in December 2012.