Official sources said it was an unscheduled meeting between the two leaders who will hold detailed talks tomorrow.
"Happy to welcome Rt Hon Shri Sher Bahadur Deuba ji, PM of close & friendly neighbour Nepal. Look forward to more extensive talks tomorrow," Modi tweeted later along with a photograph of the two.
The two prime ministers will review the entire gamut of bilateral ties tomorrow and discuss ways to further deepen the special relationship in a range of areas including trade and investment.
"The upcoming visit will provide an opportunity to both the sides for holding wide-ranging discussions on the issues of mutual interest and advancing age-old special ties of friendship between our two countries," the External Affairs Ministry had said on Monday.
More From This Section
Ever since Nepal adopted a new Constitution in September 2015, Madhesis, mostly of Indian origin, have been opposing the new statute as they fear it would marginalise them by dividing the country into seven provinces.
The blockade of trade points with India ended in February after more than 50 people were killed in clashes with the police.