Fire crews are responding to two serious house fires this morning - one in Invercargill and the other in Christchurch

Four people are hurt, two in a moderate condition, after a fire was reported just after 6am in the Invercargill suburb of Waikiwi.

Crews are also working to determine who's responsible for a house fire in the Christchurch suburb of St Albans.

Fire and Emergency Southern shift manager Mau Barbara says that blaze is being treated as suspicious.