A suicide bomber killed 27 people on Sunday when he blew himself up in a crowd of men seeking to enlist in the Yemeni army in the south-eastern city of Mukalla, medical officials said.
The Islamic State extremist group claimed responsibility for the attack, according to the US-based SITE Intelligence Group which monitors jihadist activity.
About 60 more people were injured in the blast, which took place as would-be recruits gathered at the gates of a barracks in the city, according to the officials, who spoke on condition of anonymity.
Pro-government forces and allied Gulf troops took control of Mukalla last month after the withdrawal of al-Qaeda militants who had occupied it for a year.
At least seven people were killed on Thursday in an attack, also claimed by Islamic State, on an army compound in the city.
Al-Qaeda's Yemeni branch, seen as one of the international jihadist network's most dangerous local affiliates, has also vowed to attack Yemeni government forces and members of the Gulf-led alliance backing them.
Representatives of the Yemeni government and mainly Shiite Houthi rebels, who control much of the north of the country including the capital Sana'a, are currently engaging in difficult UN-brokered peace talks in Kuwait City.
Al-Qaeda has joined the fight against the Houthis in some areas while also seeking to gain territory behind government lines in southern Yemen.
Gulf forces and government loyalists, who until recently were concentrating on the fight against the Houthis, have in recent weeks also tried to reverse al-Qaeda's gains.