Rail freight operator Aurizon has posted a 12 per cent hike in its underlying earnings to $455.6 million for the first half and says it is on track to meet its full-year guidance.

Higher revenue in its bulk and network businesses were behind the leap in 2019/20 first-half earnings before interest and tax from $406 million in the prior first half.

Aurizon delivered a 19 per cent rise in net profit to $268.9 million compared with 226.9 million at the same time last year.

The company has increased its share buyback by $100 million to $400 million and says it more than half completed.

It declared an interim dividend of 13.7 cents per share and reiterated its underlying full-year guidance for the year ending June 30, 2020, of $880 million to $930 million.