A communication system, first communication terminal, processor and base station that supports direct communication between terminals comprises a terminal that autonomously selects radio resources to be used in the direct communication, from among the candidate radio resources based on information received from the base station, performs the direct communication by use of the selected radio resources, and detects interference power after receiving the information indicating the candidate radio resources. The terminal transmits information on interference in the candidate radio resources to the base station in response to value of the detected interference power being higher than a threshold value.