Governments and airlines around the world are reviewing security procedures after two parcel bombs were found in US-bound air cargo.
Yemeni authorities announced a crackdown on all cargo shipments on Monday, while security officials manned checkpoints in Sanaa, the capital, searching vehicles and checking payments.
Yemen's national committee for civil aviation security said the measures would counteract the "methods used by terror organisations," the state news agency Saba reported.
In the UK, David Cameron, the prime minister, chaired an emergency committee meeting to decide his country's response to the scare.
Britain, the US and France have so far banned air freight from Yemen while Germany on Monday said it was extending its ban on cargo aircraft from the country to include passenger flights.
A leading al-Qaeda fighter in Yemen who surrendered to Saudi Arabia last month provided the tip that led to the thwarting of the mail bomb plot, Yemeni security officials, the AP news agency reported on Monday.
The officials said Jabir al-Fayfi, a Saudi who had joined al-Qaeda in Yemen, had told Saudi officials about the plan.
The Yemeni officials spoke on condition of anonymity because they were not authorised to talk to the press.
Several tribal leaders with knowledge of the situation, who similarly spoke on condition of anonymity, confirmed al-Fayfi's role, AP said.
The Saudi newspaper Al-Watan on Monday cited Saudi security officials saying that the kingdom gave US investigators the tracking numbers of the packages.
The parcel bombs, addressed to synagogues in Chicago, were discovered at a UK airport and in a cargo terminal in Dubai on Friday.
Qatar Airways said the Dubai parcel had been transported on two of its passenger planes from Sanaa via Doha.
Theresa May, Britain's interior minister, said the package intercepted in the UK was powerful enough to bring down the aircraft, while other officials said the device was so sophisticated that it nearly slipped past investigators despite a tip-off.
The parcel, which was hidden inside a computer printer with a circuit board and mobile phone SIM card attached, was said to contain pentaerythritol trinitrate (PETN), a highly potent explosive, which is difficult to detect in security screenings.
Fears over new security
There are suggestions that the plot could speed up calls for wider use of sophisticated imaging technology designed to detect explosives in cargo shipments.
"Cleverly concealed devices like this might suggest that there will have to be an ability for an explosive detection capacity such as CT (computed tomography)," Norman Shanks, a specialist aviation security consultant, told the Reuters news agency.
But there are fears of a knee-jerk reaction to the scare, with some pointing to potential high costs for for freight firms and others saying passenger journeys could be made more "tedious" by long checks.
At the moment only 15 to 20 per cent of cargo is screened.
Dan Nolan, Al Jazeera's correspondent in Dubai, said it would take "new and very expensive technology to be able to track this stuff down" which could have massive economic implications for the $100bn industry.
Michael O'Leary, the chief of Ryanair, told the BBC that new measures could also affect passenger flights.
"What happens, particularly in the coverage of the Yemeni issues of recent days, is that we have another huge lurch by the securicrats into making travel even more uncomfortable and an even more tedious ordeal for the travelling public," he said.
Key suspect named
In another development, US transport security investigators headed to Yemen in a bid to track down those behind the plot, as officials named a "key suspect".
Ibrahim Hassan al-Asiri, who is believed to be working with al-Qaeda in the Arabian Peninsula (AQAP) and tops a Saudi Arabian wanted list, is the brother of a suicide bomber killed last year in a bid to assassinate Prince Mohammed bin Nayef, the Saudi counterterrorism chief.
|Al-Asiri is believed to be hiding in Marib province [AFP]
"There are indications he may have had a role in past AQAP plots, including the attempted assassination of a Saudi official and last year's failed Christmas Day attack," a US official told the AFP news agency.
Yemeni security officials have also said that they are searching for al-Asiri, who is believed to be in Marib province.
Yemen freed on Sunday a woman suspected of mailing two parcel bombs destined for the US, saying she had been a victim of identity theft.
Hanan al-Samawi, a 22-year-old student, had been detained a day earlier after she was tracked down through a telephone number left with a cargo company.
But when the shipping agent was called in to identify her, he said she was not the right person. Al-Samawi is now on bail, along with her mother who was also detained.
Al-Qaeda's Saudi and Yemeni branches merged in January 2009 to form Al-Qaeda in the Arabian Peninsula.
In the past year, the organisation has emerged as "one of the most dangerous branches of al-Qaeda", according to a US assessment.
It calls for the overthrow of the Saudi and Yemeni governments and has carried out a string of brazen attacks against local security forces.
Source: Al Jazeera and agencies