Prime Minister Narendra Modi met top ministers Arun Jaitley, Venkaiah Naidu, Nitin Gadkari and Rajnath Singh to discuss election results in Delhi. The stock-taking began after a union cabinet meeting this evening, sources said.

Arvind Kejriwal and his Aam Aadmi Party have eviscerated the competition for a historic result in the capital, delivering the first major blow to PM Modi since his own spectacular election last year.

BJP chief Amit Shah is away in Ahmedabad for his son's wedding.

"The size of this victory is scary," Mr Kejriwal said in a victory speech to party workers, who showered him with petals this morning. "Let us not become arrogant," he cautioned.

Today's verdict will be particularly sweet for Mr Kejriwal, 46, who was described in the campaign for Delhi as a "back-stabber" by PM Modi, who derided him for resigning as Chief Minister of Delhi after a 49-day term. Months after that disastrous exit, Mr Kejriwal had lost the Parliamentary election in Varanasi to Mr Modi by a vast margin.

Winning power in different states is critical for the BJP and its allies to augment their strength in the Rajya Sabha or upper house of Parliament, where they are in a minority and have been thwarted in efforts to push through reforms on land acquisition, tax and other issues to revive the economy.

Since it came to power, the BJP has formed  the government in three of four states that have voted. The Delhi debacle will be dissected threadbare as the party preps its strategy for Bihar, which votes later this year.

Based on their population, states are allocated seats in the Rajya Sabha. Bihar is India's second most-populous state, after Uttar Pradesh.