BEIJING - The central government has said it will invest more than $100 billion in 23 new infrastructure projects in the underdeveloped western regions this year to boost domestic demand.

The plan was announced on Monday after Premier Wen Jiabao said the Chinese economy is 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.