BOGOTA, May 4 (Reuters) - Colombian President Alvaro Uribe has gained in popularity at home even as he fends off a scandal over illegal paramilitaries that threatens a U.S. free trade deal and military aid program, a poll showed on Friday.

Uribe's approval rating was now 75 percent, up 10 points from February as he worked to rebuff charges that some of his allies colluded with right-wing death squads, the survey by Invamer-Gallup published in El Tiempo newspaper showed.

"This is Uribe's most pronounced two-month rise in the last five years," pollster Jorge Londono told Caracol radio.

The country's strong economic growth had also helped the president, Londono said.

Uribe, a Bush administration ally, visited Washington this week to try to persuade Democrats controlling the U.S. Congress to approve a free trade agreement and more aid for Colombia despite their concerns over the paramilitary scandal.

The poll was carried out on April 21-29, just after one of Uribe's fiercest critics, Sen. Gustavo Petro, charged that the president had given tacit backing to paramilitary gangs when he was governor of Antioquia province in the 1990s.

Colombia's paramilitary movement, set up by rich landowners looking for protection from leftist guerrillas fighting since the 1960s, has been accused of some of the conflict's worst atrocities and of drug-trafficking.

Uribe, backed by billions of dollars in U.S. aid, has pushed back the rebels and negotiated the surrender of more than 31,000 paramilitaries under a deal allowing commanders short jail terms for confessing and compensating victims.

Eight of Uribe's lawmaker allies and a local governor are now in jail, charged with financing or colluding with the militias. Dozens more are under investigation.

The president denies any links to the paramilitaries.

The poll had a margin of error of 3 percent and was carried out in the cities of Bogota, Medellin, Cali and Barranquilla.

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