The Yemeni authorities have banned driving motorbikes in the southern port city of Aden where officials were shot dead by armed motorcyclists in the past few days.
Local officials said the ban was brought into affect on Tuesday and that security measures are tightened in the city which was retaken from the Houthi militants more than a month ago.
This week, a senior security officer and two military officials from the popular resistance which participated in the battles against the Houthis were shot dead separately by unidentified gunmen from on motorbikes.
The killings occurred as the local authorities are struggling to bring the situation under control after months of bloody battles.
Officials expressed fears Houthi and Qaeda sleeper cells might take advantage and seek to carry out acts of terror including targeted killings amid the ongoing battles between the pro- and anti-government forces in middle and northern regions.
Yemen has witnessed a series of targeted killings since the unrest broke out in 2011.
Hundreds of security and military officials, politicians and activists were killed mostly by armed motorcyclists.