MINING giant Xstrata has made a £5bn offer for rival Lonmin, in an attempt to boost its platinum business.

Xstrata has bid £33 per Lonmin share - a 42 per cent premium over its Tuesday closing price - and accused Lonmin's South African operations of underperforming.

Lonmin is the world's third-largest platinum producer, with the majority of its operations in South Africa.

The offer caused Lonmin shares to jump 47 per cent to 3407p - above the offer price. Xstrata shares were three per cent stronger.

Xstrata reported its own 13 per cent half-year revenues rise, with adjusted pre-tax profit flat at £2.9bn.

Chief executive Mick Davis said the offer marked the next step in the company's strategy to develop a significant platinum business and add diversification to its portfolio.

The company said the Lonmin business had been impacted by operational diff- ficulties over the past two years.