FOUR police officers were killed and one was missing after armed bandits attacked their convoy in northwest Nigeria on Friday, the Nigerian police said. Around 100 armed men attacked 16 police officers on the Birnin Gwari-Funtua highway as they returned to their headquarters in Kano state, a federal police spokesman said in a statement issued on Sunday. Armed groups of men, commonly called bandits, roam throughout northwest Nigeria, committing armed robberies, kidnappings, cattle theft and even murder. In recent months Nigerians have criticized the government for a lack of security. In December, officials said bandits kidnapped more than 300 schoolboys…