ZURICH (Reuters) - Activist investor Cevian Capital has increased its stake in Baloise Holding, it said on Monday, increasing its ability to force changes at the Swiss insurer.

Cevian now holds a position of around 9.4% in Baloise, becoming the biggest investor in the company.

The investment is an increase from the 3.12% stake held by Cevian in Baloise revealed earlier this year. According to Swiss stock market disclosures, the stake was increased to 5.11% by June.

"Baloise has the opportunity to become a top-performing Swiss insurer," said Robert Schuchna, a partner at Cevian. "We believe there is significant value potential in the company."

Cevian, which has offices in Stockholm, London and near Zurich, previously invested in Swiss engineering group ABB and last year reported a position in UBS, saying it wanted to double the value of its stake.

It has so far not revealed its plans for Baloise.

The increased stake comes after Baloise shareholders voted in April to scrap a 2% cap on voting rights, which had previously limited their influence on the company's management.

Baloise has endured a tough few years, with the Basel company's share price trailing rival insurers while investors have raised concerns the performance of its businesses outside its Swiss home market.

The company is due to publish its half-year results and give an investor update on Sept. 12, where it is expected to unveil new mid-term targets.

(Reporting by Oliver Hirt and John Revill; editing by Diane Craft)