Cameron calls for action on terrorism after bombs found
The prime minister has called for action to combat the "terrorist cancer" in the Arabian peninsula, ahead of an announcement on airport security.
David Cameron was speaking to MPs after chairing a meeting of the government's emergency planning committee Cobra.
He said the bomb's journey showed the world's interest in working together.
Home Secretary Theresa May is due to speak in the Commons after a bomb was found on a US-bound cargo plane at East Midlands airport on Friday.
Mr Cameron thanked the police and intelligence staff "whose efforts clearly prevented the terrorists from killing and maiming many innocent people whether here or elsewhere in the world".
He told MPs: "The fact that the device was being carried from Yemen to the UAE to Germany to Britain en route to America shows the interest of the whole world in coming together to deal with this.
"The threat from the Arabian peninsula and from Yemen in particular has grown.
"As well as the immediate steps which the home secretary will outline, it is clear we must take every possible step to work with our partners in the Arab world to cut out the terrorist cancer that lurks in the Arabian peninsula."
The explosive contained in the device was found at East Midlands as the result of a tip off and was not picked up by initial screening
UK officials said the tip-off came from al-Qaeda member Jabr Al-Faifi who turned himself in to Saudi authorities two weeks ago.
Investigators at East Midlands failed to realise that there was a bomb on board the flight from Yemen, before carrying out a re-examination as a precaution.
In the second search, the bomb was found hidden in a printer cartridge posted in the Yemeni capital, Sanaa.
Norman Shanks, former head of security at airport operator BAA, said cargo checks were less exacting than those on passengers.
Calling for a fundamental review of security, Mr Shanks said the industry was looking at introducing the explosive detection systems currently used for passengers' baggage that goes into the hold.
"Now this really can't be introduced for every package, but it could be used for packages coming from areas where there is a known risk," he said.
US President Barack Obama's counter-terrorist adviser John Brennan has said the US and its allies could not assume that there were no other packages containing bombs still out there.
Home Secretary Theresa May has pledged to review air freight security following the terror alert on Friday. She is due to make a statement to Parliament.
Lord Carlile, the independent reviewer of counter-terrorism laws, said the failure of existing equipment to initially identify PETN was a "weakness" and checks should be made to ensure the most up-to-date technology was in use.
The explosive used in the bomb - PETN - can be difficult to detect when well-sealed.
Lord Carlile said: "I was not in the least surprised that an attempt was made to send bombs through the parcel system which now operates on a very large scale worldwide.
"I think that we should develop the use of technology, of intelligence-led people and the use of explosive-sniffing dogs which can be very useful to ensure that no stream of exit or entry involving the United Kingdom is unprotected."
The British Airline Pilots Association said its members had been warning for years about "open-door" cargo flights.
General secretary Jim McAuslan said efforts should be switched from some of the "redundant security measures" aimed at passengers, towards checking freight instead.
"It makes no sense to us that scarce resources are used to strip down pilots with years of flying experience, rather than targeting resources at the vulnerabilities that we have seen exploited in the past 24 hours," he said.
Calls for an overhaul were echoed by the British International Freight Association, although it insisted there were "already well-established, in-depth and organised processes" in place to screen cargo.
Chief executive of budget passenger airline Ryanair, Michael O'Leary, said he feared a new raft of "ludicrous" airport security measures as a result of the latest incident.
"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."
But shadow transport secretary Maria Eagle said the bomb discovery had exposed gaps in cargo screening.
"If [it] requires extra security measures to make sure that we're safe - safe in aeroplanes and safe on the ground underneath flight paths - then, I'm afraid, that's what we're going to have to look at."
Just last week, British Airways chairman Martin Broughton called for some "completely redundant" security checks of air passengers to be abolished, highlighting the removal of shoes and separate screening of laptops.
Officials in the US said the bomb found at East Midlands - and another discovered in Dubai - were built by the same person who made the explosive device used in the failed "underpants" bomb attack over Detroit on Christmas Day.
Saudi-born Ibrahim Hassan al-Asiri - said to be the main bombmaker for al-Qaeda's Yemeni branch - was named as the prime suspect.
Meanwhile, a female student arrested in Yemen on suspicion of posting the bombs has apparently been freed.
Reports said the woman, named by human rights groups as 22-year-old Hanan al-Samawi, had no known links to Islamist militants and may have been the victim of identity fraud.
BBC security correspondent Frank Gardner said the issue of al-Qaeda in the Arabian Peninsula was key to security concerns.
He described it as a relatively small group which had reinvented itself in Yemen. The possibility that the al-Qaeda offshoot was a bigger threat than al-Qaeda in Pakistan and Afghanistan would concern the US, he said.
A spokesman for Qatar Airways said the parcel found in Dubai travelled on two separate passenger planes via the airline's hub in Doha.
The two packages were addressed to synagogues in the Chicago area. Both bombs were apparently inserted in printer cartridges.