German automotive supplier Beru has reported first-half operating profit of €22.2 million ($US28.94 million), missing analyst expectations due to one-off charges.

A Reuters survey of 10 analysts had on average expected operating profit of €26 million in the six months to September 30, little changed from €24 million a year earlier.

The news agency noted that BorgWarner has secured a majority stake in the diesel cold-start technology specialist and is offering to buy out remaining investors in a deal that values Beru at €621 million.

Beru reportedly said one-off charges of €4.2 million related to takeover advisory fees and the departure of production chief Bernhard Herzig in April had hit results.

Beru reiterated its forecast that it will boost sales and operating earnings excluding one-off items by 13% in the year to March as it benefits from rising demand for diesel-powered cars, Reuters said.

"Including these extraordinary costs, Beru aims for an operating profit of at least 59 million euros," the company said.

Reuters noted that Beru in September raised its forecast for earnings growth from its earlier goal of 10% after it bought French spark plug business Eyquem, which it will fully consolidate this year for the first time.