Dynamic coordination for task allocation in disaster environments under spatial and communicational constraints is a challenging issue in both research and applications. To this end, this paper presents a coordinated task allocation approach for disaster environments by considering spatial and communicational constraints, dynamic features of environments as well as heterogenous capabilities of agents. The proposed approach consists of an information collection mechanism, a group task allocation mechanism and a group coordination mechanism. Initially, the information collection mechanism is applied to help agents in communication networks to prune their communication connections and elect one agent in each communication network to be the network leader in a decentralised manner so as to facilitate the network leader to collect information for task allocation under communicational constraints. Then, the group task allocation mechanism is employed by each network leader to allocate tasks and agents in its network to groups with suitable spatial ranges by considering spatial and communicational constraints and heterogenous capabilities of agents. During task execution, the group coordination mechanism is employed by isolated groups to periodically adjust group members (agents) at assembly points so as to achieve continuous coordination to handle dynamic features of environments. Experimental results demonstrate that the proposed approach can have better performance than some existing approaches in terms of information collection and coordination for task allocation in disaster environments under spatial and communicational constraints.