Peruvian President Ollanta Humala's approval rating climbed to 56 percent in April, boosted by the release of energy industry workers kidnapped by Shining Path rebels, an Ipsos Apoyo poll showed on Sunday.

The president's approval rating rose 3 percentage points from the previous monthly opinion poll following last weekend's liberation of the 36 gas pipeline workers in a remote jungle region in southern Peru.

Their safe release was hailed as a success for Humala, who fought the Maoist rebels while in the army in the 1990s, though the incident has intensified pressure on him to crack down on what remains of the group.

In Sunday's poll, 66 percent of respondents said they approved of Humala's handling of the kidnapping crisis. His popularity also got a boost from the rescue of nine miners who were trapped underground for six days.

Humala's approval rating was 53 percent in March and 59 percent in February, according to Ipsos Apoyo. Humala was elected last June on pledges to include the 30 percent of Peruvians living in poverty in a decade-long economic boom.

Sunday's opinion survey, which was published in the El Comercio newspaper, polled 1,213 people in cities nationwide from April 18-20. It has a margin of error of 2.8 percentage points.

(Reporting By Omar Mariluz; Writing by Helen Popper; Editing by Will Dunham)