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"India and Nepal's ever-strengthening friendship, in the kind of global conditions that are being created today, our closeness will serve the entire humanity," PM Modi said in his address.
"I know that today when a grand temple of Lord Shri Ram is being built in India, the people of Nepal are equally happy," he added.
At their bilateral talks, PM Modi and Mr Deuba discussed ways to strengthen ongoing cooperation and develop new areas in the multifaceted bilateral partnership.
Six Memorandum of Understandings were signed by the two sides on cooperation in cultural and educational sectors.
These included the construction of the Lumbini Museum in Nepal and the establishment of the Dr. Ambedkar Chair for Buddhist Studies in Lumbini Buddhist University
Earlier today, PM Modi prayed at Maya Devi temple in Lumbini, where he was accompanied by the Nepalese Prime Minister and his spouse Dr Arzu Rana Deuba.
"I feel blessed to have prayed at the Maya Devi Temple on Buddha Purnima. May Lord Buddha bless us all and make our planet peaceful and prosperous," PM Modi tweeted soon after.
The two Prime Ministers also lit lamps near the Ashoka Pillar adjacent to the temple. Erected by emperor Ashoka in 249 BC, the pillar bears the first epigraphic evidence of Lumbini being the birthplace of Lord Buddha.
This is PM Modi's fifth visit to Nepal since 2014, but the first since the India-Nepal border row.
Relations between the two countries were strained after Nepal's previous K P Oli-led government issued a new political map in which it claimed disputed areas in the Kalapani region as its own.