CERNOBBIO, Italy (Reuters) - Oil majors are suffering after eight OPEC+ countries unexpectedly agreed to increase oil output in May, while tariffs imposed by U.S. administration had a muted effect on the sector, Eni's top executive Francesco Gattei said on Friday.

He added that energy groups could react to the possibility of tariffs denting global economic growth, reducing demand for power.

The actual increase in OPEC+ production could result lower than announced when taking into account a stricter U.S. embargo on Venezuela and the potential drop in Kazakhstan's oil flows, Gattei added, speaking on the sidelines of a business conference.