The United States has expressed concern about the Somali government's move to block dozens of lawmakers from traveling abroad.
Officials say Somali security forces prevented more than 40 parliamentarians from traveling to Kenya on Monday, where they were to discuss future elections.
A statement by the U.S. Embassy in Nairobi accused security personnel of threatening lawmakers with weapons and physically assaulting at least three of them.
The embassy said in recent weeks the transitional government has taken action "to stifle peaceful political discussion and to silence its critics."
Somali President Sheikh Sharif Sheikh Ahmed has been engaged in a very public power struggle with the speaker of parliament, Sharif Hassan Sheikh Aden.
The two men and their allies disagree on when to hold elections, and will likely square off in the contest for president whenever the elections are held.