At least 15 people were killed in the attack on the Al Qasr Hotel in Aden, according to WAM, the news agency for the United Arab Emirates.
All Yemeni government officials staying at the hotel -- including Prime Minister Khaled Bahah -- were unharmed and evacuated, Transport Minister Badr Basalma told CNN.
Four UAE soldiers were among the dead, WAM said. And the Saudi official press agency SPA said one Saudi soldier died. Both countries have contributed troops in a battle against Yemen's Houthi rebels, hoping to restore Hadi to power.
Information about what exploded, and who was responsible, varied.
Basalma said two rockets hit the building, and another landed outside. He blamed the Houthi rebels and militias loyal to ousted President Ali Abdullah Saleh
, who preceded Hadi in office.
However, the Sunni Islamist militant group ISIS claimed responsibility for the attack, which it said happened in a much different manner.
ISIS, in a statement posted on Twitter, said that suicide bombers blew up two explosive-laden vehicles at the hotel.
Basalma, explaining his belief that Houthis were responsible, cited his understanding that rockets caused the blasts.
"Only they (the Houthis) have the technical capacity to do this," he said. "These were long-range rockets with high accuracy, and it's the Houthi militias, with the technical support from Iran, who have this capability."
The officials evacuated from the hotel are staying in Aden, Basalma said.
Conflict has killed thousands
A protracted conflict has plunged the impoverished Middle Eastern nation into chaos this year.
A Saudi-led coalition, which backs the Hadi government, has been carrying out waves of airstrikes to dislodge the Houthi rebels who took control of the capital, Sanaa, earlier this year.
The Shiite Muslim Houthis are aligned with Iran
, Saudi Arabia's bitter regional rival.
At least 4,000 civilians have been killed during the war, according to the Houthi-controlled Health Ministry.
Hadi, Bahah and other members of the government returned from exile in Saudi Arabia
last month. They are based in Aden, where forces loyal to them hold sway.
Fighting between the Houthis and forces loyal to Hadi has raged across the country, enabling terrorist groups such as al Qaeda in the Arabian Peninsula
to exploit the security vacuum.