KARACHI, Pakistan - Pakistan's largest nuclear power plant was opened on Friday, generating electricity for the national grid as the country tries to wean itself off its reliance on fossil fuels.

The facility, built with Chinese assistance, in the southern port city of Karachi is Pakistan’s sixth nuclear power plant and dramatically increases its nuclear energy capacity.

China is a close ally of Pakistan and has invested billions in the energy sector, largely coal-fired power production.

At a ceremony in Islamabad, Prime Minister Imran Khan said that the plant would produce 1,100 megawatts of clean energy, taking the country’s total nuclear energy production capacity to 1,400 megawatts.

"This is important for us because Pakistan is among the top 10 countries at risk due to climate change," he said.

Pakistan has struggled with energy shortages and rising power prices.

Large-scale construction of new power plants – mostly coal-fired - has year boosted the country's energy capacity, but come with an environmental cost.

Khan said last year that Pakistan would not pursue any more power based on coal, though it was not clear the impact on a number of coal projects still being planned.

The nuclear plant was designed by China National Nuclear Corporation (CNNC) and construction started in 2015.

A seventh nuclear power plant is planned to begin operations by 2022.

(Reporting by Syed Raza Hassan, editing by Louise Heavens) ((raza.hassan@thomsonreuters.com;))