(Recasts, adds color from march)

By Hugh Bronstein

BOGOTA, July 5 (Reuters) - Much of Colombia came to a standstill on Thursday as hundreds of thousands of protesters marched against leftist rebels accused last week of killing 11 provincial lawmakers they were holding hostage.

The demonstrators took to the streets in major cities and small towns, aiming their outrage at the Revolutionary Armed Forces of Colombia, or FARC, which has long used kidnapping as a tool of war against the state.

They demanded freedom for thousands of remaining FARC hostages including French-Colombian politician Ingrid Betancourt and three American defense contractors.

"We are marching against all violence but particularly against FARC kidnappers," one young protester told Reuters in Bogota as she held a white banner saying "No More" above her head.

Colombia is in a four-decade-old guerrilla war in which thousands are killed, displaced, kidnapped and maimed by land mines every year.

Public employees were given the day off to participate in the march, during which many called for a swap of hostages for guerrillas held in government prisons. But the government and the FARC, Colombia's biggest rebel army, appeared unlikely to start talks that might lead to such an exchange.

Betancourt was captured during her 2002 presidential campaign. U.S. defense contractors Thomas Howes, Keith Stansell and Marc Gonsalves were seized by the rebels during a 2003 drug-eradication mission.

URIBE: NO SAFE-HAVEN ZONES

President Alvaro Uribe refuses to grant rebel demands that he establish a New York City-sized rural zone free of government troops where an exchange could be negotiated.

"We cannot accept safe-haven zones and we cannot accept rebels being released from prison only to go back to killing people," said Uribe, whose father was killed more than 20 years ago in a botched FARC kidnapping.

The president has long received public support for his tough stance against the guerrillas.

Thursday's edition of leading daily El Tiempo was wrapped in a supplement page with the headline "Solidarity Breaks the Chains." It featured the names in fine print of thousands of kidnap victims being held throughout the country.

The FARC was organized in the 1960s to force land reforms meant to close the wide gap that divides rich and poor in this Andean country. But even left-wing politicians say the group has scant popular support.

Last week the FARC said 11 provincial politicians held for more than five years had been killed in crossfire when an unidentified military group attacked their jungle prison.

Uribe says state security forces were nowhere near the prison and accuses the rebels of murdering the men. He wants the FARC to turn over the bodies so the circumstances of the deaths can be determined.

Colombia was stunned in 2002 when the guerrillas kidnapped the lawmakers from a government building in Cali by masquerading as soldiers and calmly escorting them onto a bus, saying they were being evacuated due to a bomb scare.

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