Dubai-based private equity firm Abraaj Capital is to invest $28 million in five start-up companies as part of its $500m investment fund for small and medium-sized enterprises, the company said on Tuesday.

The investments - the first for the Riyada Enterprise Development fund - covers sectors from healthcare to agricultural businesses, Managing Director Tom Speechley told Reuters on the sidelines of a conference on entrepreneurship.

The companies are based in Egypt, Kuwait and Jordan, Speechley said.

The Abraaj fund is working on an additional 10 investments, some of which will be concluded before the end of this year, Speechley said.

Abraaj is the Middle East's biggest private equity fund, having raised $7 billion since it started in 2002. The Riyada Enterprise Development fund was launched in 2009.