Waikato Tainui are gathering at Turangawaewae Marae to say karakia for Maori King Tuheitia Paki, who is in hospital after suffering a heart attack.
A tribal source said King Tuheitia was in Waikato Hospital but his condition was unknown.
His supporters gathered for karakia late last night at the marae in Ngaruawahia, near Hamilton, and are doing so again this morning.
Ngaruawahia local Reta Puhi Tamainupo said up to 50 people gathered at Turangawaewae marae for the solemn occasion last night.
Last week, King Tuheitia spoke about his health during his koroneihana - or annual coronation speech - at the marae.
He acknowledged his fight with diabetes and cancer, and told followers his conditions were being kept under control.