Prime Minister Narendra Modi's Hindu nationalist party clinched a landslide victory in India's most populous state of 220 million people, the Electoral Commission said on its website on Saturday.

Modi's Bharatiya Janata Party (BJP) won 311 out of 403 seats in Uttar Pradesh state, far more than the 202 seats required to form a government. Officials said the result was the biggest majority in the state for any party since 1977.

Uttar Pradesh was viewed as a referendum on Modi's first two years in office, and in particular, his decision last November to withdraw high-value banknotes from circulation in a bid to stamp out corruption. 

The initial rollout of the plan to withdraw 86 percent of currency from circulation caused economic problems and cash shortages that impacted the poor. But the government was able to address many of the problems last month as voting got underway.

"This is a victory for Prime Minister Narendra Modi's corruption-free administration and welfare measures for the poor," Modi's campaign manager, Amit Shah, said in a tweet.

The opposition Congress party and its ally, the Samajwadi Party, had hoped to capitalize on voter grievances. But early election results showed Congress, led in the state by the party vice president Rahul Gandhi, would get only seven seats. The Samajwadi Party was slated to pick up around 50 seats, a severe blow for a party that has ruled the state since 2012.

BJP was also on course for a victory in Uttarakhand state, where it was ahead in 56 out of 70 seats.

"The BJP has reached new heights in Uttarakhand and Uttar Pradesh states and changed the political picture of the country," said India's home minister, Rajnath Singh.

Congress party faired better in Punjab state, where it won 77 of 117 seats. The BJP and Congress failed to win majorities in western Goa state and northeastern Manipur state, according to the Election Commission.

Victories in Uttarakhand and Uttar Pradesh will have an impact on the upper house of parliament, where a number of Modi's reforms, including a national sales tax, have stalled.

Its make-up is based on parties' strength at the state level and the BJP is currently a minority.

cw,mm/rc (AFP, AP, Reuters)