Dawn staff reporter and senior journalist Hasan Mansoor passed away on Thursday in Karachi. He was 54.

Mansoor, who had over three decades of journalism experience and remained associated with a number of reputable news organisations, passed away in his sleep at his residence.

According to family sources, the journalist suffered a heart attack. His funeral prayers will be offered after Friday prayers at Masjid-e-Khizra near the Sindh High Court.

Take a look: Hasan Mansoor's reporting for Dawn

He left behind a son, a daughter and a widow. He was the youngest among six brothers.

Besides being a veteran journalist, Mansoor was also a short-story writer and poet. Prior to his demise, he was writing a novel on Karachi, with particular focus on the Lyari neighbourhood.

His friend and journalist Jan Khaskheli said Mansoor started his journalism career from Sindhi newspaper Awami Awaz in 1988, for which he used to write a weekly satire column. In some of his short stories, he used to focus on the human tragedy of violence in Karachi. He used to say that if his short stories were compiled, they would be published in three books, Khaskheli recalled.

A graduate of the University of Karachi, Mansoor worked as a staff reporter for Daily Times newspaper for five years before joining daily Dawn in 2006 and working until 2008. He also worked for The Star newspaper and served as a correspondent for French news agency Agence France-Presse for over a decade.

He later rejoined Dawn newspaper where he covered social and political issues.

Journalists and colleagues expressed shock and grief at his sudden death. Taking to Twitter, they recalled Mansoor as a "smart", "hard working", "funny" and "full of life" person.

Sindh Chief Minister Murad Ali Shah also expressed grief at his death. While recalling Mansoor as an honest journalist, Shah prayed for the departed soul, according to his spokesperson.