Attacks in Russia's Dagestan grab international attention after Boston

• A daily summary of global reports on security issues.

Six people, including two teenagers, were reportedly killed in two separate attacks in Dagestan, a Russian region in the Caucasus mountains plagued by an ongoing Islamic insurgency.

Independent Russian news agency Interfax reports that two teenagers died when a bomb planted in a package exploded outside a housewares shop in the Dagestani capital of Makhachkala today.  The package had been left on the side of the road near the shop, and the teenagers, aged 15 and 17, were killed trying to open it, according to a Dagestani interior ministry official. Two other teenagers were wounded in the explosion.

State news agency RIA Novosti adds that a third man died later from the blast, which police said was equivalent to two kilograms (4.4 pounds) of TNT.

And Agence France-Presse reports that three police officers were killed last night in the city of Buinaksk when their cars came under attack by gunmen.

"Unidentified persons ... opened automatic gunfire" at the two cars the policemen were travelling in, said a statement on the Investigative Committee website.

"Two more policemen were taken to the hospital with various wounds," the statement said.

Dagestan and the rest of the Caucasus republics of Russia have been the site of a long-running Islamic insurgency against Moscow and its local allies. In 1999, Russian forces invaded Chechnya, located just west of Dagestan, to squelch a regional separatist movement. Over the years, the movement has radicalized into an Islamist terrorist operation, which has launched repeated deadly attacks over the years both in the Caucasus and against the Russian homeland, including Moscow itself.

The Causasus have come under greater scrutiny from the West recently, due to the Boston Marathon bombers' connections with the region. The parents of Tamerlan and Dzhokhar Tsarnaev both live in Dagestan, and in 2012, Tamerlan reportedly visited relatives there. Neither brother registered on Dagestani security forces' radar however, The Christian Science Monitor reported.

The Dagestani Interior Ministry, the main law enforcement body in the Caspian republic of Dagestan, where Tsarnaev spent as many as seven months in 2012 visiting relatives, said in a statement Saturday that "the Tsarnaev brothers are not on our databases of those wanted."

The independent Interfax agency quoted a source in the Chechen security service as saying that "according to our information, these people did not appear on the republic's territory." Interfax also quoted a senior security source in Moscow, presumably from the FSB secret service, as also denying any knowledge of the Tsarnaevs. "Since the brothers Tsarnaev lived outside Russia, our special services were unable to provide our foreign partners with any operationally relevant information," the source is quoted as saying.