The incident in Lodhdri village of Rapar taluka, nearly 500km from here, took place on Tuesday but was reported today.
The deceased were identified as Parbatbhai Koli (aged around 25), her son Mana (4) and daughter Sharda (1), Rapar Station House Officer (SHO) Harish Bhatt said.
Parbatbhai was washing clothes outside her hut when she heard screams of her kids who were inside the house which had caught fire, he said.
She rushed to save them but all three perished in the blaze, the SHO said, adding her husband, a casual labour, was out when the tragic incident took place.