A new branch of the Islamic State group in Yemen on Thursday issued a video showing what it said was the beheading of four Yemeni soldiers and the shooting of 10 others, the SITE Intelligence group reported.

Islamic State in Yemen has claimed responsibility for attacks before, and has issued an online film showing it conducting training, but Thursday's video, attributed to the group's branch in Shabwa province, is its first to show killings.

The film did not say when the killings took place, but before their execution the men spoke to the camera saying they were from the Yemen army's Second Mountaineer Brigade. Local media reports had said 14 soldiers from that unit were massacred in mid-April, the U.S.-based SITE monitoring service said.

The video, shot at night, showed a group of men kneeling on the ground with masked figures behind them. It then showed four bodies with a severed head on the chest of each before showing the other men being shot in the head with an assault rifle as they knelt.

In a separate statement on a jihadi Twitter account, another Islamic State group in Yemen's Hadramawt region said it had raided an army checkpoint in the town of Tarim, causing the soldiers to flee.

Al-Qaida in the Arabian Peninsula (AQAP), al-Qaida's Yemeni wing, has killed hundreds in attacks across the country in recent years and has taken advantage of fighting in recent months to consolidate its hold in eastern regions.

Analysts have voiced fears that advances by the Houthi militia, whose members are mainly from the Zaydi Shiite sect regarded by Sunni jihadis like Islamic State and AQAP as heretics, might bring a more openly sectarian edge to Yemen's messy civil war.