The PM was addressing cheering party workers at the BJP office in Delhi. He arrived there on Saturday evening for a meeting of the parliamentary board, the BJP's highest decision making body, after most results had been announced. "People of Meghalaya, Nagaland and Tripura have spoken," PM Modi had tweeted, adding, "Tripura election is an epoch-making one."

Earlier in the day, party chief Amit Shah said the BJP and its allies in the NDA are now in power in 21 states, pointing out that he was not counting Meghalaya, where it is not clear yet who will form government. Saturday's wins were an endorsement of Prime Minister Narendra Modi's leadership, Mr Shah said.

But, said the BJP chief, he would still not define this as his party's "golden period." That would come, he said, "when the party wins Odisha, Kerala and West Bengal," adding that he is confident the BJP will post a big win the Karnataka assembly elections in a few months from now.

The BJP, along with its regional ally the IPFT, has won 43 of Tripura's 60 seats. The party on its own got 35 seats; it had won no seat in 2013. The Left won 16, losing 35 from last time. A party needs 31 seats to win a majority. State BJP chief Biplab Kumar Deb, 48, is widely expected to be the BJP's pick for chief minister in Tripura.

Left party the CPM conceded defeat in Tripura saying in a statement, "BJP has, apart from other factors, utilized massive deployment of money and other resources to influence the elections." In Tripura, the CPM lost an important citadel on Saturday after 25 years in power. It now rules only one state - Kerala.

In Meghalaya, the Congress has won 21 seats, 10 short of the halfway mark at 31. It has sent top leaders Kamal Nath and Ahmed Patel from Delhi to talk to regional parties for support. "Associates have assured support in the last one hour. The BJP is out of the fray, they are trying to create mischief," said Kamal Nath to NDTV.

The BJP and its regional allies in Meghalaya like the National People's Party (NPP) and the United Democratic Party are contesting separately. The party's senior strategist Himanta Biswa Sarma is in state capital Shillong to work out a post-poll alliance.

In Nagaland, the BJP and its regional partner NDPP won 29 seats, two less than the majority mark. But late in the evening, Independent candidate Tongpang Ozukum and the Janata Dal (United) Nagaland decided to support the BJP, reported news agency ANI, taking their numbers to 31, the majority mark in the 60 seat assembly. The NPF of Chief Minister TR Zeliang also won 29. The BJP had pulled out of an alliance with the NPF and chose to ally with Mr Rio's new party.

Saturday's results further consolidate the BJP's position in the northeast, recently bolstered by the party forming government in Assam, Manipur and Arunachal Pradesh.