The fate of three Colombian hostages has been the focus of international attention after rebels offered in December to release them.

The hostages are: Clara Rojas, a former vice-presidential candidate; her young son, Emmanuel, who is believed to have been fathered by one of her captors; and a former congresswoman, Consuelo Gonzalez.

But on 31 December, an international mission led by Venezuela to oversee the release was suspended amid mutual recriminations.

The fate of these and other hostages is still far from clear.

Exactly how many hostages are held by the rebels?

It is hard to say but it is thought the Farc are holding up to 800 hostages in secret jungle lairs. Many of these people have been taken for ransom to help pay for the guerrillas' operations. Among the captives are some 45 high-profile hostages who are considered "exchangeable".

The rebels want to exchange these hostages, who include police and military officers and politicians, for some 500 guerrillas imprisoned in Colombian jails.

Who are the hostages?

Many of the people seized by the rebels are police and soldiers.

The most high-profile captive is Ingrid Betancourt, who was kidnapped along with Clara Rojas in 2002 as she campaigned for the presidency.

The fate of Ms Betancourt, 45, has received international attention because of her dual French-Colombian nationality. Her family have also mounted a very vocal and visible campaign in France to keep her name in the headlines. French President Nicolas Sarkozy has also been active in efforts to secure her release.

Also among the group considered "exchangeable" are three US nationals, who were working for a US defence contractor when their small Cessna plane went down in a rebel-held area in February 2003.

Marc Gonsalves, Keith Stansell and Thomas Howes were employed by Northrop Grumman and were involved in anti-drugs surveillance missions.

What is the condition of the hostages?

This is very hard to say as there has been so little news about them.

One of the most dramatic developments came in November 2007 when the Colombian authorities released videos and photos of 16 high-profile hostages, the first sign of life since 2003.

The material, which included letters apparently written by the hostages, had been found with captured rebels, officials said.

Among those shown were Ms Betancourt, sitting in a jungle setting and looking very thin. The three Americans were also on tape as well as 12 other hostages, mostly members of the Colombian security forces.

Some of the material appeared to be recent, dated October 2007.

In July, rebels delivered a video to a Colombian journalist, in which seven hostages pleaded for the government to talk to their captors.

Many of the hostages shown in this video have been held for nearly 10 years. Among them was soldier Pablo Emilio Moncayo, whose father this year walked across Colombia in chains in an attempt to put pressure on the guerrillas and authorities to negotiate the hostages' release.

And in May, a Colombian policeman, John Frank Pinchao, emerged to say he had escaped the rebels after nearly nine years in captivity.

He said he was held in a camp with the three US nationals and Ms Betancourt.

What are the prospects for the hostages' release?

The fate of the hostages must be seen within the context of the overall conflict in Colombia and the many unsuccessful attempts to negotiate an end to the fighting.

All the armed groups, including the smaller National Liberation Army (ELN) and right-wing paramilitary groups, have been drawn into kidnapping and the illegal drugs trade.

President Alvaro Uribe has pursued a hardline stance against the Farc, who are regarded as a terrorist group by the US and the European Union.

In 2007, Mr Uribe released some rebel prisoners, as a "goodwill gesture" and has offered to designate a safe zone to allow negotiations to take place on securing a prisoner exchange.

He insists that any Farc prisoners who are freed from jail must agree not to take up arms again.

The Farc are demanding that the authorities demilitarise a large area of south-western Colombia to serve as a "meeting point" for the proposed exchange of some 45 hostages for 500 imprisoned rebels.

What role has Venezuela's President Hugo Chavez been playing?

Mr Chavez became involved in official efforts to broker a swap four months ago, being seen as someone to whom the Farc rebels could talk.

In November, however, Mr Uribe ended his mediation efforts, saying the Venezuelan leader had overstepped his mandate by talking directly to Colombian military chiefs.

This led to a distinct cooling of ties but the Venezuelan leader continued his involvement in the hostage issue.

On 18 December, the Farc announced that they would release Clara Rojas, her son and Consuelo Gonzalez to Mr Chavez or someone designated by him.

On 26 December, Mr Chavez unveiled a plan to send Venezuelan aircraft to Colombia to pick up the three hostages from a site to be stipulated by the rebels.

His request that the Colombian authorities allow Venezuelan aircraft to enter their territory was granted, with the condition that the planes and helicopters used carried the markings of the International Committee of the Red Cross.

Why was this operation suspended?

International envoys flew to the Colombian city of Villavicencio amid growing hopes that the guerrillas would free the hostages.

The plan was for the rebels to then convey information on where exactly the hostages would be turned over.

But on 31 December, Mr Chavez read out a statement said to be from the Farc in which they said continuing operations by the Colombian army had impeded the hostages' release.

Mr Uribe said the rebels were lying. The real reason, he indicated, was that the rebels no longer had the boy, Emmanuel.

On 4 January, the Farc admitted that Emmanuel was indeed the boy who had been identified living in foster care in Bogota.

DNA tests carried out using blood from Ms Rojas's mother had showed that the boy almost certainly was Emmanuel.

He had been handed over to child welfare authorities in San Jose del Guaviare in June 2005, and then transferred to the Colombian capital.

The latest twist will give the rebels and the government even less reason to trust each other than before. They could both be tempted to toughen their stance in any negotiations about the hostages' fate.

The failure of the mission has also shown up the already tense ties between Mr Uribe and Mr Chavez, who accused the Colombian leader of "sabotaging" the rescue effort.

It also shows the limits of Mr Chavez's influence on the rebels.