By Marc Frank

HAVANA (Reuters) - Peace talks between the Colombian government and the Revolutionary Armed Forces of Colombia, or FARC, resumed in Havana on Wednesday in hopes of ending the 50-year-old bloody conflict even as fighting and bickering continued.

Negotiators took a break last week from the first round of talks which began in November and which seek an end to the last Marxist-led armed rebellion in South America, considered a vestige of the cold war.

They arrived Wednesday at the Cuban capital's convention center in a city suburb.

For the first time, government negotiators entered through a back door, avoiding reporters, while the FARC read a long declaration to the press about the war and the human and economic damage it has wrought.

Comments earlier this week by a FARC negotiator that the group was still holding "prisoners of war" brought harsh words from the government's lead negotiator, Humberto de la Calle, despite denials by two other rebel negotiators.

"The FARC has to respond to the victims, it has to clarify this issue of kidnapping, the way to deal with the issue of kidnapping is not with ambiguities," he said before departing Colombia for Cuba.

The FARC seized dozens of politicians and members of the armed forces over the years to use as bargaining chips with the government. Such high-profile captives have since been released.

But the families of civilians taken to fund the FARC's war say scores of people remain in jungle camps and the group continues to kidnap despite a pledge this year to cease taking captives for ransom.

Colombian forces killed at least 20 FARC guerrillas in an air and ground raid near the border with Ecuador at the weekend, the army said on Monday, the deadliest strike against rebels since the peace process started.

"It seems normal to us that at the start the positions are far apart. The effort is to put to the test the art of stringing pearls ... bring positions closer together, loosen them and build outcomes satisfactory for the sides," the FARC declaration said.

The statement did not mention the hostage issue or the raid.

Colombia's government has vowed to keep up military operations and not allow the rebels to rest and recoup, as they did during previous failed talks more than a decade ago. The FARC has called a two-month ceasefire.

FARC negotiator, Jesus Carvajalino, alias Andres Paris, told Reuters, "the raid was the government's Christmas present while we continue with the cease fire."

Colombian President Juan Manuel Santos is hoping a decade of U.S.-backed blows against the FARC has left the group sufficiently weakened to seek an end to the war.

The FARC is banking that the damage its 9,000 fighters can still inflict on South America's fourth largest economy is enough to garner significant concessions from the government.

Cuba and Norway are acting as guarantors of the talks which are broaching some of the root causes of the conflict such as agrarian development, drugs, political participation of opposition groups and victims' reparations.

Santos said at the weekend that the discussions should not drag on for too long and must be completed by November 2013 or earlier. The rebels have said they would remain in negotiations as long as necessary.

(Additional reporting by Nelson Acosta, Helen Murphy in Bogota; Editing by Jackie Frank)