China has said it will invest more than 100 billion dollars this year in 23 new infrastructure projects in impoverished western regions as part of efforts to boost domestic demand.

The plan was announced Monday after Premier Wen Jiabao said the Chinese economy was facing an "extremely complicated" situation and two purchasing manager surveys showed manufacturing activity had slowed in June.

The 682.2 billion yuan will be used to build railways, roads, airports, coal mines, nuclear power stations and power grids, the National Development and Reform Commission said on its website.

Construction will start this year to "actively expand domestic demand and promote the fast and healthy development of the western areas," the top economic planning agency said.