India's economy expanded by a blistering 8.4 per cent between July and september, putting the south Asian nation into the ranks of the world's fastest-growing economies, official figures showed Wednesday.

Growth for the second quarter of the year to March financial year was driven by agriculturedependent India's most abundant monsoon rains in a decade.

The numbers came as good news for the ruling Hindu nationalist Bharatiya Janata Party (BJP) which is expected to call early elections in April or May to cash in on the "feel-good" feeling stemming from the economic boom.

The figures put Asia's third-largest economy firmly on track to achieving the government's growth target of seven per cent for the fiscal year, economists said.

"It's mainly the agriculture sector that helped. I expect growth to be around seven to seven and a half per cent for the full year," D.H. Panandikar, economist at the RPG Foundation in Delhi, said.