Leighton shares gained over four per cent after the construction giant said its first half profit would come in higher than forecast.

Leighton said improved earnings from its Australian and Asian operations would help deliver an underlying profit of about $270 million in the six months to December 30.

That is above the company’s previous forecasts of an underlying profit of $250 million.

Net profit for the six months to the end of December is expected to be about $340 million.

That would be up 57 per cent from the same period in 2010, with the growth due to a $169 million after tax gain on Leighton’s sale of its HWE Mining iron ore business to BHP Billiton in late 2011.

Leighton shares were among the best performers in the market’s top 200 stocks, gaining 91 cents, or 4.43 per cent, to $21.44 on Monday.

But the shares remain well below their level of 12 months ago of $30.80.

Leighton posted a loss of $408.8 million for the 12 months to June 30 last year, due in part to delays to Brisbane’s airport link project and a Victorian desalination plant.

Chief executive Hamish Tyrwhitt said progress had since been made on those projects.

“The performance of our major projects – Airport Link and the Victorian desalination project – has stabilised and we are making good progress in bringing them to completion,” he said in a statement.

Airport Link will be opened to traffic in June this year, and first water will be produced by July, Mr Tyrwhitt said.

Leighton also confirmed its expectations for an underlying profit of between $600 million and $650 million for the 12 months to June 30.

The six months to December 31 represents a transitional period for Leighton, as it moves from reporting for a financial year that ends on June 30 to a year that ends on December 31.