TOKYO, July 24 (Reuters) - World handball champions Denmark started their bid to capture back-to-back Olympic gold medals by thrashing hosts Japan 47-30 in their opener at the Yoyogi National Stadium on Saturday. Denmark rode on three-times World Player of the Year Mikkel Hansen"s five goals to end the first half with a 25-14 lead as Japan, who are competing in men"s handball at the Games for the first time since Seoul 1988, struggled to get into the contest. The Danes sent a warning to their rivals by increasing the pressure in the second half to complete a comprehensive win, as Jacob Holm finished with nine goals and Magnus Saugstrup with eight. It was a tighter opener for Sweden, who beat Bahrain 32-31 in Group B as the world championship runners-up edged ahead with 52 seconds left though Albin Lagergren"s goal, before Andreas Palicka saved Mohamed Ahmed"s penalty. "They played aggressive (with a) high defence we normally don"t see in Europe that much, so it"s harder for our players... to adjust in one game," Sweden left wing Hampus Wanne said. "It"s good we scored 32 goals, but we let in 31... a lot of credit to Bahrain, they did a great job in defence and attack." European champions Spain pipped Germany 28-27 after Philipp Weber failed to convert a free throw towards the end of the match, while dark horse Egypt defeated Portugal 37-31. Earlier, France playmaker Nikola Karabatic, back after seven months out due to a knee injury, inspired the two-times Olympic champions to a 33-27 win over Argentina. The 37-year-old came on at halftime with the Rio 2016 silver medallists up 12-10 and immediately won a penalty, before fellow substitute Melvyn Richardson scored seven goals from as many shots as Guillaume Gille"s side cruised. Norway made a slow start and trailed Group A rivals Brazil in the first half before finding their groove to prevail 27-24 for their first win at the Games since 1972, as Sander Sagosen top-scored with eight goals. "It was a nervous start but that"s normal," said Norway coach Christian Berge, who turned the match around by replacing goalkeeper Torbjorn Bergerud with an outfield player in an aggressive seven-on-six attack. "In the second half we did better but still didn"t play like ourselves. Hopefully we"ll see that in the next game. We have to be better in our attack against Spain."