Nato scrambled fighter jets twice in two days to intercept Russian military aircraft over the Baltic Sea, it said on Tuesday as Russian military activity in the region was reported to be increasing. Lieutenant Colonel Robert Gericke said the Russian aircraft were flying in international airspace and had not violated the territory of alliance members. Two Canadian F-18 Hornet jets were scrambled from the Siauliai base in Lithuania on Monday to intercept a Russian Ilyushin-20 surveillance aircraft, which they shadowed for 15 minutes, Nato said. Earlier, the Latvian military reported that Nato F-16 jets were dispatched on Tuesday to intercept a Russian Ilyushin-20 over the Baltic Sea. Gericke confirmed that Nato jets had also intercepted a Russian aircraft that day, but could not provide more details. Nato, which has 16 fighter jets monitoring Baltic airspace, said it regularly launched jets to identify "unknown or potentially hostile aircraft" in the proximity of national airspace. There were two similar incidents in the region on October 7 and September 11, but on neither occasion did the Russian aircraft constitute a threat to Nato forces, the alliance said. Since Friday, the Swedish navy has been searching the Stockholm archipelago for signs of a foreign submarine that officials suspect entered its territorial waters illegally. It hasn't officially linked Russia to the suspected intrusion. The Finnish military says Russian military aircraft have violated its airspace five times this year.