MOSCOW // Two blasts hit Russia's Caucasus, one killing a policeman at a checkpoint and the other wounding about two dozen at a street cafe, in the latest attacks to rock the turbulent region. In the first attack, a young man blew himself up near a checkpoint in the region of North Ossetia, killing himself and a policeman, officials said. Hours later, at least 22 people were wounded in a suspected car bomb explosion outside a cafe in the spa town of Pyatigorsk, popular with Russian holidaymakers, in the foothills of the Caucasus mountains. The Kremlin calls the Caucasus unrest its biggest domestic problem and Prime Minister Vladimir Putin last month announced an ambitious drive to foster prosperity by enticing investors to the violence-torn region. In North Ossetia an unidentified man walked up to the checkpoint close to the administrative border with neighbouring Ingushetia and detonated his charge, leaving one officer dead and wounding two others, said Samir Sabatkoyev, spokesman for the regional interior ministry. "He detonated an unidentified explosive device," Sabatkoyev said. "He blew himself up," he added, noting it was "apparently" a suicide attack. The two wounded policemen had "serious injuries", added Maria Gatsoyeva, a spokeswoman for regional investigators, speaking from the regional capital Vladikavkaz. North Ossetia lies to the north of the breakaway Georgian region of South Ossetia, recognised by Russia as independent after the brief 2008 war with Georgia over its status. The region is part of the country's most volatile North Caucasus region, scene of the simmering guerrilla war between Russian forces and separatist rebels, and deadly attacks in the republics of Chechnya, Ingushetia and Dagestan are a near-daily occurrence. The explosion in Pyatigorsk struck around 1230 GMT, the investigative committee of prosecutors said. Russian news agencies quoted the emergencies ministry as saying that 22 people were wounded. Glass windows within a radius of 200 metres (219 yards) around the outdoor cafe were broken and cars parked by the cafe were damaged by the power of the blast. "At first it was thought that it was a gas explosion but then it became clear that a car parked outside the cafe had exploded," a local police source told ITAR-TASS. "All the wounded were customers of the cafe," the source added. Pyatigorsk lies to the north of the most unstable mountainous regions of the Caucasus and is a genteel town normally untroubled by such violence. President Dmitry Medvedev ordered a full investigation into the incident, Russian news agencies said. In January, the Kremlin appointed a new envoy responsible for the North Caucasus, businessman Alexander Khloponin, who devised a plan to turn around the regional economy. But Medvedev last week lashed out at Khloponin, saying at a meeting on the economic situation in Dagestan that changes were slow to come and "nothing is moving." Militants from the Caucasus were blamed for the bombings on the Moscow metro on March 29 carried out by two female suicide bombers that killed 40 people in a pair of coordinated attacks. * Agence France-Presse