Betsi Cadwaladr University Health Board says an increase in demand for emergency care in its hospitals across North Wales has led to "significant pressures".
Some surgery will now be suspended to relieve the strain on hospitals. The health board added that the situation is being reviewed "on a daily basis".
Detectives investigating historic sex abuse at children's homes in North Wales today arrested a 52-year-old man from Mold on suspicion of child cruelty and indecent assault, the National Crime Agency said.
A report written 17 years ago after claims of abuse at children's homes in North Wales during the 1970s and 1980s concluded that the abuse was "extensive" and took place over a "substantial number of years".
The Jillings Report, which focused on allegations of abuse within the North Wales council care system, was compiled in 1996 but was shelved by the former Clwyd County Council because insurers feared compensation claims.
A heavily edited version of the report has now been published online in the wake of fresh investigations into the abuse.
A £250 million super-prison that could hold up to 2,000 inmates will be built in North Wales, Chris Grayling announced.
The Justice Secretary said the new jail is expected to bring around £23 million a year to the regional economy and create around 1,000 jobs.
Mr Grayling first discussed plans for a super-prison in January as he announced a raft of prison closures covering some 2,600 inmate places.
Chief Secretary to the Treasury Danny Alexander confirmed to the Commons that £100 million would be invested in the construction of the prison in 2015/2016 as part of a multi-billion investment programme.
The project will ultimately receive £250 million of investment from the Government.