A court in Yemen's southeastern city of Mukalla sentenced 13 Somalis each to 12 years in jail on Saturday after convicting them of piracy, a judicial source said.
The men, whose trial had started in October last year, were found guilty of seizing two Yemeni boats in the Gulf of Aden to use as mother ships from which to launch attacks on merchant vessels.
Yemen's navy said in May it nabbed the 13 Somali pirates and liberated a fishing boat and its crew four days after they were seized near the island of Socotra in the Gulf of Aden.
The Arabian Peninsula country's forces recovered weapons including machine guns and two rocket-propelled grenade launchers.
On May 18, a court in the capital Sanaa sentenced six Somali pirates to death and jailed six others for 10 years each for seizing a Yemeni oil tanker and killing two cabin crew in April 2009.
A day later, a court in the southern port city of Aden sentenced 10 Somali pirates to 10 years in jail for trying to hijack a cargo ship in Yemeni waters.