BBC journalists and other employees today began a 24-hour strike over job cuts that has seriously disrupted live programming on television and radio.
The National Union of Journalists (NUJ) and two other unions representing technical workers were striking to protest plans by BBC director general Mark Thompson to cut about 20 per cent of its workforce, or about 4,000 jobs.
BBC One's Breakfastprogramme was running with a basic service and one presenter.
Its flagship Todayprogramme on Radio 4 was replaced by a pre-recorded programme on music, and BBC 2's Newsnightis expected to be cancelled later today.
BBC News 24 and BBC World switched to recorded news bulletins after midnight, although they later resumed some live news broadcasting.
The NUJ said staff for the foreign-language service of the World Service had also joined the picket line.
The broadcaster said it regretted the strike action and would do everything it could to produce the best possible service.
"Industrial action will not remove the need for further consultation or the need for the BBC to implement changes which will enable us to put more money into improved programmes and services," it said in a statement.
Local BBC programmes on both TV and radio in Northern Ireland were severely disrupted today by strike action.
The BBC1 Newsline programme was blacked out and on Radio Ulster Good Morning Ulster, Talkback and the Steven Nolan Show were both cancelled and replaced by reruns of old programmes.
The 24-hour nationwide strike was in protest at BBC plans to cut nearly 4,000 jobs, about 100 of them in Northern Ireland. Notice has also been given to the BBC management of a 48-hour stoppage next week.
Three journalists' and technicians' unions, Amicus, the National Union of Journalists and Bectu were involved in the strike - the biggest at the corporation in more than a decade - and mounted a picket line at the BBC base in Belfast's Ormeau Avenue.
An NUJ spokesman said the strike action had not been taken lightly, but staff felt they had been left with no choice. By taking programme off air the unions hoped management would realise the depth of concerns about where the BBC was going.
"They're planning to get rid of at least 98 members of staff but they want to keep the same amount of programmes and output. "That means more pressure on the staff left behind - and stress levels are already high. "We have tried to get management to listen but they seem determined to plough ahead with changes without consulting staff here.
In reality the BBC, that we're all proud of, is being torn apart." The Irish Congress of Trade Unions said it strongly supported the strike.
"This strike is not just about redundancies. It is about the ethos of the BBC and the fight to preserve the highest quality in public service broadcasting at a time when there is a need to preserve the independence and integrity of journalism," said the ICTU.