Unidentified gunmen attacked Guinea-Bissau's interior ministry and presidential palace on Saturday, killing two policemen and wounding 10 others, the interior minister and a senior security official said. Security forces repelled the attack, which took place shortly before 0600 GMT. Interior Minister Al Adji Mumini Embalo told reporters that 10 attackers and 10 other suspects had been arrested, Reuters reported. "We don't know the motive of the attack and who is behind it," he said. "But the situation is already under control." The deputy director of state security, Abdu Camara, said two of those arrested had attacked the presidential palace, which is less than 100 metres (yards) from the interior ministry building in central Bissau. In a statement, the army said the dawn raid was an isolated incident with no link to members of the military or paramilitary forces. It appealed for calm and said the army had been put on maximum alert. The former Portuguese colony is on edge ahead of a July 24 presidential run-off between Malam Bacai Sanha of the main PAIGC party and former military ruler Joao Bernardo Vieira. --More 2244 Local Time 1944 GMT