NAIROBI, Kenya — A Navy SEAL team targeted a senior leader of the Shabab militant group in a raid on his seaside villa in the Somali town of Baraawe on Saturday, American officials said, in response to a deadly attack on a Nairobi shopping mall for which the group had claimed responsibility.

The SEAL team stealthily approached the beachfront house by sea before exchanging gunfire with militants in a predawn firefight that was the most significant raid by American troops on Somali soil since commandos killed Saleh Ali Saleh Nabhan, a Qaeda mastermind, near the same town four years ago.

The unidentified Shabab leader is believed to have been killed in the firefight, but the SEAL team was forced to withdraw before that could be confirmed, a senior American official said. Such operations by American forces are rare because they carry a high risk, and indicate that the target was considered a high priority. Baraawe, a small port town south of Mogadishu, the Somali capital, is known as a gathering place for the Shabab’s foreign fighters.