Mark Davies, the Communications Director for the Post Office, said: "We apologise to our customers who are being inconvenienced by the strikes today."
He added that the Post Office's transformation plan aimed to reduce the company's losses by investing in Crown offices.
More top news
The garden of paedophile friends of serial killers Fred and Rosemary West is being dug up by police after a tip-off.
A man has been arrested on suspicion of murder after a woman's body was found in south Wales.
After the Indiana polls close, ITV News asked Ted Cruz supporters if they could back Donald Trump as the Republican presidential nominee.