A top US intelligence officials has said that terrorists, armed lethal weapons and latest communications gadgets, entered Mumbai -- for November 26 attack -- through sea route to avoid any detection and "they were successful". "The Mumbai attackers entered the city via the sea because they believed it was the best route to avoid detection," Charles E Allen, Under Secretary for Intelligence and Analysis and Chief Intelligence Officer of the US Department of Homeland Security told a Congressional committee on Thursday. The Senate Committee on Homeland Security and Government Affairs convened a hearing on Mumbai terrorists attacks. "Sea infiltration permitted the attackers to come ashore with a substantial cache of weapons that might have been detected during a land entry to the city. They were able to locate precise landing points by using Global Positioning System (GPS) for navigation," he said testifying before the committee chaired by Senator Joseph Lieberman. Analyzing the Mumbai attack in depth, Allen said the terrorists and its perpetrators were able to ascertain routines and its vulnerabilities of the security forces at the primary targets during the pre-operational phase. "The attackers were able to fend off the Indian response force because they were heavily armed with automatic rifles and grenades the weapons of basic infantryman. The group reportedly received extensive training that may have included urban assault operations," Allen said. In addition, the attackers used communication devices, including satellite phones and cell phones to coordinate movement activities, establish defensive positions, repel rescuers and resist Indian efforts to suppress them. "Also many of the security cameras installed inside the hotels were not operational during the period of attack," he added.