NEW DELHI, March 23 (Xinhua) -- Indian Prime Minister Narendra Modi wrote a letter to his Pakistani counterpart Imran Khan, greeting him on the occasion of Pakistan's national day, confirmed an official source in the Indian external affairs ministry on Saturday.

Pakistan's national day is celebrated every year on March 23.

"Prime minister sends customary message on national days to other heads of state or government. His message to Prime Minister Imran Khan highlighted the importance of a terror free Asia," said the official source.

Imran Khan also tweeted about receiving message from Modi. "Received message from PM Modi: 'I extend my greetings and best wishes to the people of Pakistan on the National Day of Pakistan. It is time that people of sub-continent work together for a democratic, peaceful, progressive and prosperous region, in an atmosphere free of terror and violence.'"

The letter assumes significance in the wake of escalating tension between the two countries since February.