SB 4.10.5

gatvodīcīṁ diśaṁ rājā
 rudrānucara-sevitām
dadarśa himavad-droṇyāṁ
 purīṁ guhyaka-saṅkulām
Synonyms: 
gatvā — going; udīcīm — northern; diśam — direction; rājā — King Dhruva; rudra-anucara — by followers of Rudra, Lord Śiva; sevitām — inhabited; dadarśa — saw; himavat — Himālayan; droṇyām — in a valley; purīm — a city; guhyaka — ghostly persons; saṅkulām — full of.
Translation: 
Dhruva Mahārāja went to the northern direction of the Himālayan range. In a valley he saw a city full of ghostly persons who were followers of Lord Śiva.
Purport: 

In this verse it is stated that the Yakṣas are more or less devotees of Lord Śiva. By this indication the Yakṣas may be taken to be the Himālayan tribes like the Tibetans.