China has agreed to lend Pakistan $6.5 billion to help build nuclear power stations including a 2,200-megawatt plant in Karachi, as Beijing increases its involvement in the cash-strapped country.

Prime Minister Nawaz Sharif announced the package at a briefing on Wednesday, saying it would help ensure an uninterrupted power supply.

The loans are to be provided by Chinese state-owned Exim Bank and will be repaid at a concessional rate over 20 years, according to reports.

A finance ministry spokesman confirmed the deal to AFP on Thursday.

It is the latest example of Chinese involvement in Pakistan, which is battling to get its shaky economy back on track and solve a chronic energy crisis that cripples industry.

Pakistan began building the 2,200-megawatt plant, set to be its largest nuclear power station, last month with Chinese technical assistance.

The country faces an electricity shortfall of around 4,000 megawatts in the sweltering summer, leading to lengthy blackouts that make ordinary people's lives a misery and have strangled economic growth.

Chinese companies are working on more than 100 major projects in energy, roads and technology, according to Pakistani officials, with an estimated $18 billion expected to be invested in coming years.

Aside from the 2,200 MW project Chinese companies built two of Pakistan's three operational reactors.

Chinese engineers are also busy in the construction of a 969 MW hydropower project in Kashmir. They have also committed to generate 6,000 MW of electricity from coal and wind in the southern province of Sindh.