In the message recorded from his home, he said doctors were not allowing him to go out in the evening following treatment for pneumonia.
The general made his unprecedented statement in a videotaped message which was shown to his supporters during his 85th birthday celebrations on Friday night.
In the video, he described his 16 months of detention in London as very sad.
General Pinochet returned to Chile from house arrest outside London in March, after the British authorities deemed him too ill to stand trial in Spain, where a judge had requested his extradition.
He is now facing more than 170 charges in Chile for alleged human rights abuses between 1973 and 1990.
The authorities in Argentina are also seeking his extradition in connection with the killing of an exiled army general in Buenos Aires.
Suffering
General Pinochet did not attend a birthday gathering of hundreds of his supporters in Santiago.
In the message recorded from his home, he said doctors were not allowing him to go out in the evening following treatment for pneumonia.
Sitting beside a small Chilean flag and a photograph of his wife, General Pinochet hesitantly said: "As an ex-president, I accept responsibility for all the deeds that the army and armed forces are said to have committed."
He did not elaborate further on the matter of political responsibility.
'Disagreeable' arrest
Most of General Pinochet's birthday speech focused on his detention in London.
He described his arrest as very "disagreeable".
"But I had the dignity to say I was not complying with English because I had a country whose justice system was just as good."
"I suffered pains, I suffered sadness, and sirs, I suffered much sadness in my heart," he added.
Mental fitness
General Pinochet was arrested in London in 1998 under a warrant issued by a Spanish judge seeking to try him for human rights abuses during his years in power.
He was released by Britain on health grounds, but returned to Chile to face a growing number of charges against him
Last August, the Chilean Supreme Court stripped him of the immunity he enjoyed as a senator for life.
But before any trial can go ahead, General Pinochet must undergo medical tests to determine if he is mentally fit.