(Adds details from results)

Aug 10 (Reuters) - Colombian financial conglomerate Grupo Aval reported a 28.9% year-over-year fall in net profit in the second quarter Wednesday, with profit sliding to 675.5 billion pesos ($157 million) dragged down largely by an increase in interest expenses.

Interest expenses jumped 111.6% from the year-ago period.

The company said interest income in the April to June period hit 4.29 trillion pesos, up 36.3%, driven by the improvement of the quality of its financial portfolio and a rise in revenues from its non-financial businesses.

The conglomerate's portfolio includes Colombian banks Banco de Bogota, Banco Popular, Banco AV Villas and Banco de Occidente.

In the first quarter, the company more than doubled its year-on-year net profit linked to the spin-off of a subsidiary.

($1= 4,309.69 pesos) (Reporting by Valentine Hilaire and Noe Torres)