Sana’a: Yemeni authorities impounded 500 illegal motorbikes in a three-day campaign to put an end to hit-and-run shootings which killed dozens of security officers last year, officials said on Monday.

“The campaign has succeeded in stopping 500 unlicensed motorbikes and 72 cars without number plates, some of which are suspected to have been used in assassinations,” an interior ministry report said, adding that 50 weapons such as Kalashnikovs and other firearms were seized during the crackdown.

“Motorbikes have become a headache for security forces as extremist groups use them to assassinate security officials,” General Abdul Rahman Hanash, a high-ranking interior ministry official, told reporters.

The interior ministry says that 40 members of the security forces and four civilians were killed in 2012 in hit-and-run shootings by gunmen on motorbikes.

Sana’a security chief, Omar Abdul Karim, said that “terrorist groups” have used the unrest in Yemen “to reorganise their ranks and launch a series of hit-and-run assassinations.”

There are more than 200,000 motorbikes across Yemen, most of which are unregistered, according to Sana’a police.

Some 103 police patrols took part in the campaign, which began in Sana’a on Saturday, according to the ministry.

Residents said that police checkpoints were set up across the capital at which vehicles and motorbikes without number plates were stopped.

Passersby were also searched for unlicensed weapons in the country where gun ownership has long been a key part of culture.

Yemen has an estimated 60 million firearms in private hands, roughly three for every resident.

Al Qaida in the Arabian Peninsula has been blamed for most of the killings although it has not claimed responsibility for any of the assassinations.

AQAP took advantage of the weakness of Yemen’s central government during an uprising in 2011 against the now forced out president Ali Abdullah Saleh, seizing large swathes of territory across the south.

But a month-long government offensive that ended in June pushed most of the militants to the more lawless desert regions of the east.