Ad hoc wireless networks offer anytime-anywhere networking services for infrastructure-free communication over the shared wireless medium. The proliferation of portable devices and ad hoc networks have led to the need for security services. This is illustrated daily in the media with reports of wireless network vulnerabilities. In this setting, secure group key agreement and efficient group key management are considered challenging tasks from both an algorithmic and computational point of view due to resource constraint in wireless networks. In this article, we present two dynamically efficient authenticated group key agreement protocols by reflecting ad hoc networks in a topology composed by a set of clusters. We analyse the complexity of the schemes and differentiate between the two approaches based on performance in a wireless setting. The proposed protocols avoid the use of a trusted third party (TTP) or a central authority, eliminating a single point attack. They allow easy addition and removal of nodes, and achieve better performance in comparison with the existing cluster based key agreements. Additionally, our proposed schemes are supported by sound security analysis in formal security models under standard cryptographic assumptions.