By Henri Astier and Steve Rosenberg, BBC News, London & Moscow
An area sealed off by police following deadly attacks in Russia's North Caucasus region of Dagestan, seen in a screengrab of a video released by Russian state news agency RIA Novosti. Photo: AFP Photo / RIA Novosti
Gunmen in Russia's North Caucasus republic of Dagestan have killed six police officers in a series of attacks, security officials say.
A synagogue, two churches and a police checkpoint were targeted in the cities of Derbent and Makhachkala. Twelve other officers were wounded.
A Russian Orthodox priest has also been killed and four attackers shot dead, state media report.
The assailants have not been identified, but Dagestan has in the past been the scene of Islamist attacks.
Footage posted on social media shows people wearing dark clothes shooting at police cars, before a convoy of emergency service vehicles arrive at the scene in Makhachkala, Dagestan's largest city.
In Derbent - home to an ancient Jewish community - gunmen attacked a synagogue and a church. Both buildings were set ablaze, local officials say.
An unofficial channel on the Telegram messaging app, Mash, said gunmen were barricaded in a building in Derbent.
Russia's Investigative Committee launched an investigation over "acts of terror", AFP news agency reported.
Later on Sunday, police detained Magomed Omarov, a prominent local politician who head of the Sergokalinsky district, following reports that two of his sons were among the attackers.
Dagestan is a predominantly Muslim republic. It is also one of the poorest parts of Russia.
Less than a week ago the deputy head of the FSB, Russia's domestic security service, chaired a meeting in Makhachkala to discuss "anti-terrorism measures". The aim was to boost security of "transport, hotels and other mass public areas".
In April the FSB arrested four people in Dagestan suspected of involvement in the attack on Moscow's Crocus City Hall venue the previous month.
More than 140 people were killed in that attack, which was claimed by the Islamic State group.
Between 2007 and 2017, a jihadist organisation called the Caucasus Emirate, and later the Islamic Emirate of the Caucasus, staged attacks in Dagestan and the neighbouring Russian republics of Chechnya, Ingushetia and Kabardino-Balkaria.
- BBC