The BBC has been banned for a third time from covering an official panel's investigation into the final phase of the Sri Lankan civil war.
But the BBC correspondent and a number of Sri Lankan journalists were turned away at the prison gates.
The 26-year conflict ended in May last year with victory for government forces over the Tamil Tiger separatists.
The BBC's Charles Haviland says Boosa jail holds about 700 Tamil Tiger suspects, some of whom have been detained for years without trial.Sri Lanka bans BB CFullStory