The death toll rose to 20 on Monday from two seemingly coordinated attacks by gunmen in Russia’s southern republic of Dagestan, Russian investigators said.

Wielding rifles and Molotov cocktails, the attackers assaulted synagogues and Orthodox churches on Sunday night in two major cities of Dagestan, a predominantly Muslim region in the northern Caucasus Mountains.

The dead included at least 15 law enforcement officers and some civilians, regional officials said. The local health authorities said an additional 26 people had been injured.

For hours, the gunmen were on the loose, exchanging shots with members of law enforcement, according to statements from the region’s interior ministry. Five attackers were eventually killed, local officials said.

Russian investigators designated the assault an act of terrorism, but it was not immediately clear who was responsible or whether they were specifically targeting law enforcement officers.

One of the civilians killed was Nikolai Kotelnikov, an Orthodox priest in the city of Derbent. The attackers also set fire to a synagogue in the city.

The Kremlin spokesman, Dmitri S. Peskov, said that President Vladimir V. Putin was receiving regular reports on the attack but did not plan to address the nation about it. Mr. Peskov declined to comment on the gunmen’s motives.

Without public guidance from the Kremlin, many pro-government commentators on Monday attempted to present the Dagestan attack as part of Russia’s broader lone standoff against the vague, dark forces of a hostile world. This narrative of national victimhood has become increasingly prevalent in Mr. Putin’s Russia since the invasion of Ukraine.

“What we are seeing is the Russian regime’s latest episode of the loss of control in the most diverse places — places that are often unexpected to the government itself,” Mr. Baunov wrote on the Telegram messaging app on Monday.

An upsurge in extremist violence in Russia in recent months has dented one of the main legacies of Mr. Putin’s 25-year rule — a brutal pacification of the restive Northern Caucasus region that brought safety to Russian cities at the cost of empowering local strongmen and squashing human rights.

In March, four gunmen killed 145 people at a concert hall near Moscow in an attack claimed by the Islamic State. It was the deadliest terrorist attack in Russia in more than a decade. The United States had given Moscow a fairly specific advance warning about the attack.

In Dagestan last October, a mob, apparently searching for Jewish passengers, stormed a plane arriving from Tel Aviv.

And earlier this month, several men detained on terrorist charges led a short-lived prison mutiny in the southern Russian city of Rostov-on-Don. The mutineers took local guards hostage and claimed affiliation to the Islamic State in videos — not independently verified — that were published on social media from smuggled cellphones. They were killed by Russian special forces who stormed the prison hours later.

According to Tanya Lokshina, an associate director for Europe and Central Asia at Human Rights Watch who has been working on Dagestan for more than 20 years, the Sunday attack was a “glaring failure of the security services” that have been too distracted by the war in Ukraine.

In a phone interview, Ms. Lokshina said that Dagestan’s pervasive security apparatus is “unable to control the situation now,” because their resources and Moscow’s attention are focused elsewhere.

Russian officials tried to mask intelligence failures surrounding the Moscow concert hall attack by blaming the West and Ukraine, without providing evidence. And initial statements by officials after Sunday’s attack suggested that the government may adopt a similar tactic in Dagestan.

“We need to understand that war comes into our home,” Mr. Melikov added.

Mr. Peskov, the Kremlin’s spokesman, in his daily news briefing on Monday appeared to draw a connection between the Dagestan violence and a separate attack by Ukraine on Sunday on occupied Crimea.

Local officials declared a three-day mourning period in Dagestan, a multireligious and ethnically diverse region, and said families of the victims would receive special compensation.

Dagestan’s roughly 3.2 million residents are split among dozens of ethnic groups. The largest groups are predominantly Muslim, but the region is also home to a significant Christian minority, as well as a small Jewish community, one of the oldest in Russia.

Dagestan underwent a period of intense violence in the early 2000s, a product of the spillover from an anti-Russian insurgency in the nearby Chechnya region and local mafia wars. The specter of that period, when deadly attacks on law enforcement were nearly a daily occurrence in Dagestan, led the Kremlin to reassure the country that Sunday’s attack was an isolated tragedy.

Russia’s antiterrorism committee, which coordinates the fight against terrorism in the country, said in a statement that two attackers had been killed in Derbent and three more in Makhachkala. It said that law enforcement officers were looking for accomplices.

The investigators did not disclose their identities.

But Russian state media and Kremlin propagandists said that among the attackers were relatives of a local official and a member of a prominent martial arts club, a major sport in Dagestan.

The investigative agency also posted a video showing burned cars, guns in pools of blood and heavily armed security service officers chasing the apparent perpetrators inside an Orthodox church. The video could not be independently verified.

Mr. Melikov said a manhunt would continue in the republic until “all members of extremist sleeping cells” that were “undoubtedly prepared also from abroad” were caught.