One of Pakistan's best known Sufi musicians, Amjad Sabri, has been shot dead in the southern port city of Karachi, triggering an outpouring of grief over what police have described an "act of terror".

Sabri was shot several times on Wednesday while driving in his car in the city's Liaqatabad area, when a motorcycle pulled up alongside the vehicle and the attackers opened fire, Pakistan's English language newspaper Dawn reported.

The 45-year-old singer is survived by wife and five chidlren.

Sabri's brother, who was also in the vehicle, was wounded.

"Two riders used 30-bore pistols to shoot Sabri five times. The bullet to the head took the qawwal's life. The attackers took the Hassan Square route to escape," Inspector General Mushtaq Mehar told Dawn.

"It was a targeted killing and an act of terrorism," Muqaddas Haider, a senior police officer told AFP news agency, without naming possible suspects.

Nawaz Sharif, Pakistan's prime minister, condemened the singer's killing and ordered an investigation.

His killing was met with shock and condemnation. Neighbours congregated outside the singer's home to offer condolences to his relatives, while TV channels broadcast recordings of his music in tribute.

A splinter faction of the Pakistani Taliban has claimed responsibility for the killing, saying Sabri's qawwalis were blasphemous.

Fakhre Alam, the Chairman of the Sindh Board of Film Censors, claimed on Twitter that Sabri had earlier submitted an application for security, but the home department refused to follow up on it.

Amjad Sabri had submitted an application for protection as per his family but Home department did NOTHING...Shameful & disgusting — Fakhr-e-Alam (@falamb3) June 22, 2016

Asghari Begum, Amjad Sabri's mother told Al Jazeera, that about six months ago three unknown assailants came to their residence and had burst open the front door. Amjad was not present, and they had left.

Sabri and his late father, Ghulam Farid Sabri, were well-known qawwali singers - a style of music rooted in Sufism, or Islamic mysticism - that is popular across South Asia with roots tracing back to the 13th century.

Sufi mosques and shrines have come under attack in recent years, including the 2010 bombing of the Data Darbar shrine in Lahore that killed more than 40 people.

Additional reporting by Alia Chughtai in Karachi