Five Al-Qaeda militants have escaped from a prison in the western Yemeni city of Hodeida, a security official in the capital said without providing details.
Authorities distributed pictures of five men and urged people who had any information concerning the whereabouts to contact security services.
The jail break came as Omani foreign ministry official Saeed Badr bin Hamad al-Busaidi said his country was investigating reports that Al-Qaeda militants had infiltrated the tiny Gulf sultanate from eastern Yemen.
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The countries share a long border through desert and mountainous regions.
Al-Qaeda has been on the defensive since the Yemeni army recently overran its strongholds in the south and east of the country following a month-long campaign.
On Saturday, the army took control of the southeastern town of Azzan, a known Al-Qaeda bastion, deserted by the militants a week earlier.
According to several sources, the fighters who fled Azzan, in the southeastern Shabwa province, have sought refuge in an eastern region of Yemen close to the border with Oman.