By Mauro Orru

Iberdrola SA said Monday that it has increased its offer for the acquisition of renewable-energy provider Infigen Energy to around 869 million Australian dollars ($596.6 million).

The Spanish utility company said it decided to raise its offer to AUD0.89 per security in cash, from AUD0.86 previously.

Iberdrola's move comes after UAC Energy Holdings raised its offer for Infigen Energy to AUD0.86 per stapled security.

Write to Mauro Orru at mauro.orru@wsj.com; @MauroOrru94