China's Shanghai Electric plans to spend $9 billion overhauling electricity infrastructure in Karachi, a minister told AFP, just months after the multinational revealed it was buying a Pakistan power company.

China is ramping up investment in its South Asian neighbour as part of a $46 billion project unveiled last year that will link its far-western Xinjiang region to Pakistan's Gwadar port with a series of infrastructure, power and transport upgrades.

In a presentation made to Pakistani authorities, Shanghai Electric said it would invest an average of $700 million a year until 2030 to increase capacity, improve cabling and target bill defaulters.

"The investment would be utilised in distribution, generation, transmission" and training, Miftah Ismail, minister for state and chairman of Pakistan's Board of Investment told AFP on Wednesday.

The investment would also aim to tackle widespread electricity theft and other losses that cost about $269 million a month in the city, partly by replacing above-ground grid stations with underground ones.

Shanghai Electric announced in August it would buy a majority stake in K-Electric, which is owned by Abraaj Group of Dubai, for $1.7 billion, which would be Pakistan's biggest ever private-sector acquisition.

K-Electric, formerly known as Karachi Electricity Supply Corporation, supplies electricity to more than 2.2 million households and commercial and industrial consumers.