Prime Minister Nawaz Sharif called an emergency meeting of a cabinet energy panel on Tuesday to discuss the power outages .

In a statement, the Prime Minister's Office said the meeting focused on "urgent measures" to reduce power cuts during Ramzan, which coincides this year with summer temperatures forecast in some regions at around 40 degrees Celsius (104°F).

Sharif came to power four years ago promising to end scheduled blackouts - known as "load shedding" - that have plagued daily life for years, hobbling the economy and deterring foreign investment.

Higher power generation has helped ease load shedding in many areas in recent months, but technical breakdowns in the past week have boosted the frequency and length of blackouts, sparking anger during the blistering late summer months.

Protests erupted on Tuesday in Karachi after electricity was cut during the pre-dawn feast Muslims hold before they begin fasting from daybreak to sunset.

Some protesters tried to attack and set fire to an office of the city's main power provider, K-Electric, said police officer Khadim Ali.

A transmission line had tripped due to high humidity, K-Electric said on Twitter, adding that the load shedding would persist for two to three weeks more.

Sindh Chief Minister Murad Ali Shah blamed the ruling Pakistan Muslim League-Nawaz (PML-N) government. "This is the atrocity the federal government is doing with us," Shah told reporters.

On Monday, two demonstrators were killed in another protest against electricity shortages in Khyber Pakhtunkhwa, reportedly when police fired to disperse crowds.

One of those killed was shot by police and later died in hospital in the Malakand district, said Humayun Khan, the provincial representative of Pakistan People’s Party (PPP).

Both deaths were being investigated, said the district's deputy commissioner, Zafa Ali Shah.