Yemen says captured soldiers were studying in Syria
Yemen's defence ministry has denied that five military officers reportedly being held by rebels in Syria were sent to fight alongside government forces.
An official told BBC Arabic that the soldiers had been studying at a military academy in Aleppo and were detained as they tried to travel home.
The al-Nusra Front, an Islamist rebel group in Syria, posted a video on Sunday saying it had captured them.
The video showed five men asking Yemen to stop supporting Bashar al-Assad.
The Yemeni defence ministry said the five soldiers had travelled to Syria two years ago to study at the Assad Military Academy in Aleppo as part of a military co-operation agreement between the two countries.
They were detained on 4 September as they travelled from Aleppo to Damascus to get their flight home, it added.
The ministry's account supports what the Yemeni human rights group, Hood, told the Reuters news agency over the weekend.'Cut all ties'
The unverified four-minute video, which was posted on jihadist forums, shows the identity cards of five men, one of whom appears to be a lieutenant-colonel, as well as pictures of them in military uniform.
The men are pictured sitting below a black flag emblazoned with "al-Nusra Front" in Arabic.
The video includes an interview with one of the men, who says the group had been sent to Damascus to help quell the uprising.
The man, who identifies himself as Mohammed Abdo Hezam al-Meleiky, says: "I ask the Yemeni government to cut all logistical and military ties because Bashar al-Assad's regime is a regime that is killing its people and that is what we saw with our own eyes when we came here."
The al-Nusra Front is a shadowy jihadist group which says it has been behind many of the bombings that have rocked Syria since January 2012.
Opposition activists say more than 27,000 people have died in the violence since protests against President Bashar al-Assad began in March 2011. The UN puts the death toll at more than 20,000.
Yemen's government - which is battling its own Islamist insurgency - has not publicly criticised the tactics used by the Syrian authorities.
Last November, Yemen was one of just three Arab League states - along with Syria and Lebanon - to vote against suspending Syria from the bloc.
There have been recent reports in Yemen suggesting that supporters of former Yemeni President Ali Abdullah Saleh are fighting alongside Syrian government forces, and that supporters of the uprising that forced him to hand over power last year are fighting alongside Syrian rebels.