Islamabad, July 1 (IANS): Pakistan Prime Minister Nawaz Sharif flew to the mega port city of Karachi on Wednesday, where a relentless heat wave has killed more than 1,200 people over the past 10 days.

Sharif presided over a meeting of senior officials on the "recent intense heat wave in Karachi and the resulting casualties", a PM office press release said.

The prime minister was informed that the heat wave hit Karachi on June 19 and more than 65,000 patients were reported in Karachi hospitals during this period, out of which more than 1,200 lost their lives.

"Most of those who lost their lives were homeless people, including beggars, whose dehydration was aggravated due to fasting during Ramadan in the extreme weather," an official said at the meeting.

Hundreds of people were still being treated in at least four government-owned and private hospitals, the provincial health departments said.

Opposition parties criticised authorities in Karachi for failing to launch a campaign to ensure that people should not be exposed in the sun when the severe heat wave was approaching. The meteorological department argued that a break in the routine sea breeze in the city of nearly 20 million people caused the heat wave.

The frequent power outages and shortage of water in Karachi were also blamed for the high number of deaths.

Sharif described the heat wave as "unprecedented in the history of Pakistan" and promised that all departments which "shirked their responsibilities adding to public misery would be held accountable in a transparent manner".

The prime minister said lessons should be learnt from such calamities and measures should be taken to avoid their recurrence in the future.

Officials said hundreds of shelters have been set up by local authorities, the military, political parties and social welfare groups to treat the affected people.

Director of Pakistan Meteorological Department Muhammad Hanif said high humidity and low wind caused the severe heat wave.