"It is a very sad news. I am really upset ever since I heard this news. Not only me, the entire world loved his songs. There is no doubt about it that he was an outstanding singer," Mangeshkar said.
In 2010, Tera Milana, a duet by the two legends was launched as part of an album named 'Sarhadein'. While Hassan recorded it in Pakistan in 2009, Mangeshkar later heard the track and recorded her part in India in 2010. It was later mixed together for a duet.
Hassan, known for ghazals like Ranjish hi sahi, Patta patta, boota boota, passed away at a Karachi hospital after a prolonged illness. He was 84.
Lata, 82, says they shared mutual respect.
"I have shared a very good relationship with him. I really respect him a lot and even he used to respect me a lot. I have met him just two to three times, he was a wonderful human being."
"Gaana ek aisi cheez hai jo sabko nazdeek rakhta hai... Gaanewale hamesha nazdeek ke hi hote hai (Music keeps everyone close, and singers are always close to one another)," added Mangeshkar.
She also took to twitter to share her emotions and wrote that Hassan "brought an important change in ghazal segment" and that it would be difficult to "find an artist" like him.
"Wo bohot bade shastriya sangeet ke gayak bhi the, aur unke gaane me Rajasthan ke sangeet ki khushboo bhi thi," she wrote and added that he composed songs for her.
"Unhone mere liye kuchh gaane banaaye the, unme se hi ek ghazal jo unhone mujhe gaake bheji thi, uska maine duet karke record kiya tha. Unke saath mera ye ek hi gaana hai (He had composed some songs for me. Of these, one ghazal which he sang and sent to me, I recorded as a duet. That was my only song with him)," she wrote.
"Main ishwar se prarthana karti hun ki Mehdi sahab ki aatma ko woh shaanti pradan karein (May his soul rest in peace)," she added.