"Spoke to @capt_amarinder & congratulated him on the win in Punjab," PM Modi tweeted.
His tweet came as the Congress party was heading towards forming the government in Punjab.
The ruling Shiromani Akali Dal-Bharatiya Janata Party combine received a major drubbing in these Assembly elections.
Spoke to @capt_amarinder & congratulated him on the win in Punjab. Also wished him a happy birthday & prayed for his long & healthy life.Narendra Modi (@narendramodi) March 11, 2017
PM Modi also wished Mr Singh on his 75th birthday, which falls on the same day.
The Congress leader was born on this day in 1942 in Patiala, Punjab.