* Rebels urge government to agree to ceasefire
* Government says rebel actions send wrong signal for peace
* Talks began in November, no major advances yet
By Jeff Franks
HAVANA, Jan 31 (Reuters) - Colombia and the Marxist FARC rebels resumed peace talks on Thursday to end their half century-long conflict amid new tensions after the guerrilla group resumed kidnappings and attacks that sparked an angry government reaction.
The rebels, as they entered the negotiations at a Havana convention center, urged the government to agree to a ceasefire to stop the violence that threatens to scuttle the peace process.
Government negotiators did not comment as they walked past reporters. On Wednesday the leader of their delegation Humberto de la Calle blasted the FARC, or Revolutionary Armed Forces of Colombia, for its latest hostile actions in Latin America's longest-running insurgency.
The two sides have been negotiating off and on since November seeking to end a war that dates to the FARC's founding in 1964 and in which tens of thousands of people have died and millions have been displaced.
The talks, which the government wants to wrap up in a year, have increasingly degenerated into a public war of words, and no major advances toward peace have been announced.
Military sources on Thursday accused the FARC of kidnapping three oil workers, killing four soldiers and blowing up an energy tower.
They were accused earlier of kidnapping two police officers.
Lead FARC negotiator Ivan Marquez said he did not know how the case of the two policemen will be handled because there has been no official confirmation they were abducted by his group.
De la Calle on Wednesday blasted the FARC for the kidnappings, rejected a ceasefire and accused the guerrilla group of trying to prolong the war.
"The signal they are sending with this kidnapping is completely contrary to what they should be doing," he said.
The FARC has a long history of kidnapping for ransom, but said last year it would end that practice and now hold only captured Colombian security force members whom it considers as legitimate "prisoners of war."
The FARC called a unilateral ceasefire at the start of the talks in November, but halted it Jan. 20 after the government refused to join the truce.
President Juan Manuel Santos has vowed to maintain military operations against the FARC, which has been weakened by a decade-long military offensive backed by the United States.
The two sides are trying to resolve some of the basic issues behind the war, including Colombia's history of social inequality.
They have been discussing land reform proposals that would distribute land to the rural poor. (Editing by David Adams and Andrew Hay)