Nearly 300 have died in four major hospitals in the port city of Karachi, the provincial capital, a senior health official, Saeed Mangnejo, told the media.
Meteorological officials say the temperature in Karachi reaches 45 degrees which is a record since 1979.
Head of the Karachi’s main state-run Jinnah Hospital, Dr Semi Jamal, said 200 people died in her hospital. She said a vast majority of those dead were above 50 years of age.
She said over 3,000 affected people were brought to hospital over the past three days. Around 200 were stated to be in critical condition.
On Monday, scattered rains had to some extent decreased the temperature.
Prime Minister Nawaz Sharif has expressed deep grief and sorrow over the deaths caused by severe heat in Karachi, the PM office has said.
In a statement, he said those hospitalized should be given best possible medical treatment.
He directed the concerned authorities to create awareness among people about the current situation of heatwave in order to avoid more deaths.
Nawaz Sharif directed the ministry of water and power to keep him updated about the latest power supply situation.
The paramilitary force “Pakistan Rangers” has established ten ” Heat Stroke Relief Centers” at different locations in Karachi to provide relief to the citizens who are affected due to extreme heat wave, officials said.
The doctors, paramedical staff and complete medical facilities will be available at each center to cure heat stroke patients.
The Human Rights Commission of Pakistan has called for urgent interventions to prevent further loss of life.
“The authorities must play their part in enhancing consciousness of how to minimise the hazards of exposure to the sun while going about everyday activities,” the Commission said in a statement.