At least 12 people have been killed and another 18 injured in two bomb blasts in Russia's volatile North Caucasus region, two days after a deadly attack on Moscow's transport network.
The first blast occurred in the town of Kizlyar in the southern province of Dagestan on Wednesday morning, when car bomb near a school was detonated, killing two police officers.
Rashid Nurgaliyev, Russia's interior minister, said the bomb went off as police tried to stop the suspicious-looking car.
He said as police and residents gathered at the scene of the blast a suicide bomber, wearing a police uniform, approached and detonated a set of explosives.
A high proportion of those killed were policemen, authorities said, including the town's police chief.
The blasts come just two days after twin suicide bomb attacks in Moscow's metro system killed 39 people and injured scores.
Escalation in violence
Russian officials have blamed Muslim separatist fighters from the North Caucasus for those attacks.
Neave Barker, Al Jazeera's correspondent in Moscow, said there are fears that the bombings in Moscow and Dagestan are pointing to an escalation in violence in Russia.
"The parallels are quite striking between the attacks in Dagestan and Moscow," he said.
"This morning the federal security service said the two female suicide bombers that blew themselves up in Moscow may have been acting as part of a group of up to 30 more suicide bombers.
"The security service believes they could have been recruited and trained by a man called Said Buryatskiy, or Alexander Tikhomirov, who was a well-known Chechen warlord.
"He was killed in a special operation by Russian forces at the beginning of March.
"Officials have said that both of these attacks may be a revenge for the killing of one of their principal commanders in the field."
The North Caucasus has been the site of two wars in Chechnya and hundreds of violent attacks since the 1991 collapse of the Soviet Union.
Violence has spread from Chechnya to the neighbouring regions of Dagestan and Ingushetia.
Speaking to Al Jazeera, Magomed Mutsolgov, a human rights worker in Ingushetia, said: "There will be some tighter security here, more police checks, even rough violent checks, not just because of what happened in Dagestan but also in Moscow.
"And across all the north Caucusus there will be more raids, and lots of checks of suspicious people.
"There will be various lists – relatives of people who died, relatives of militia, relatives of victims.
"I'm sure there will be more violations, persecutions and discomfort for people. To put it mildly. I don't doubt this will happen".
'War is coming'
In February, Doku Umarov, the leader of a Chechen opposition group, said in an interview on a separatist-affiliated website that "the zone of military operations will be extended to the territory of Russia".
Umarov, who claimed responsibility for the bombing of a passenger train travelling between Moscow and St Petersburg in November, warned that "the war is coming to their cities".
Monday's attack - the deadliest in the Russian capital in six years - has fuelled fears of a broader offensive by separatists based in the North Caucasus.
Vladimir Putin, Russia's prime minister who led Moscow into a war against Chechen separatists in 1999, said on Tuesday that those behind the bombings must be
scraped "from the bottom of the sewers" and exposed.