Accuracy in detection of landmines and intelligent deployment of sensors are two major determinants for an automated landmine detection system. Wireless sensor networks (WSNs) based applications can be very effectively used in military applications for detecting the landmines that are laid down by the enemy. Accurate mine detection in such application is very important otherwise it may lead to loss of life. Prompted by this we propose an adaptive sensor placement algorithm where sensor placement is dynamically determined based on existing mine concentration in a given area thus ensuring that sensors are localized in the region of higher mine concentration. We further use clustering algorithm for data aggregation from sensor nodes reported from high mine density region; this ensures optimum utilization of sensor batteries which is one of the major determinants in sensor lifetime and hence system reliability. Simulation is done for adaptive sensor deployment and data aggregation using cluster formation in areas of varying mine concentration to check the effectiveness of our proposed algorithm.