More than 40 people including women and children have been shot dead aboard a boat carrying Somali refugees in the Red Sea off war-torn Yemen, officials said on Friday.
A sailor who had been operating the boat, Ibrahim Ali Zeyad, said 80 refugees were rescued after the incident.
While the identity of the helicopter was not immediately clear, Saudi Arabia, which is leading a coalition in the war in Yemen, has US-built Apache A-64 Longbow attack helicopters.
Various pro-Houthi media outlets have reported the helicopter was bombing various rebel positions on the Yemeni coast at the time of the attack, but there has been no comment or confirmation from the Saudi-led coalition in Yemen.
The UNHCR said that as conditions worsen in Yemen, refugees are starting to use areas further to the north as a transit route.
Saudi spokesperson General Ahmed al-Asseri justified the attack by claiming the area, Hudaida, is "illegally" under the control of the rebels.
He said about 75 men and 15 women who survived the attack were taken to detention centres, and some bodies were laid in a fish market in the town of Hodeida because of a lack of space in mortuaries.
An Arab coalition was assembled by Saudi Arabia in 2015 to fight the Houthis and troops loyal to former President Ali Abdullah Saleh who have fired missiles into neighbouring Saudi Arabia.
The Saudi war on Yemen has killed thousands of civilians, and unleashed a humanitarian crisis in the improvised Middle Eastern country. They finally managed to hold up flashlights and show the helicopter they were poor migrants.
Refugees reportedly killed by Apache helicopter.
Al-Hassan Ghaleb Mohammed told the Associated Press news agency the refugees were trying to reach Sudan after leaving Ras Arra.
The coastal province has been under heavy airstrikes over the past two years since the coalition joined the conflict in support of the government. The attack was among the deadliest throughout the violent Saudi-led, US -backed military campaign against Shiite Houthi rebels in Yemen that began in 2015.