Prince Tomohito of Mikasa, Emperor Akihito's eldest cousin, was taken early Thursday to a Tokyo hospital after suffering an irregular heartbeat, the Imperial Household Agency said.

The 58-year-old prince is now in stable condition and is expected to stay for a few more days at Keio University Hospital in Tokyo's Shinjuku Ward, the agency said.

Doctors said the prince showed symptoms of an accelerated form of atrial fibrillation, which means the upper part of the heart beats faster than the rest of the organ. His pulse has since recovered.

According to the agency, Prince Tomohito had complained of symptoms similar to heatstroke and was subsequently hospitalized from July 6 to 11 at a different hospital in Tokyo where he was given intravenous drips.