Yemen launched a major operation on Tuesday to arrest a Saudi bomb maker accused of being behind a foiled bomb plot involving US-bound parcels as the poverty-hit Muslim nation came under pressure to find those responsible.
With the military deploying, suspected al Qaeda militants blew up an oil pipeline in southern Yemen operated by a South Korean firm on Tuesday, a local official said. It was not immediately clear if exports from the small oil producer would be affected.
The aim of the military operation in the provinces of Maarib and Shabwa was to capture suspected bomb maker Ibrahim al-Asiri, and the US-born radical preacher Anwar al-Awlaki, who is wanted by Washington for his links to al Qaeda, a Yemeni security official said.
Yemeni authorities also began the trial in absentia of al-Awlaki, who has been linked to the failed bombing of a US-bound plane in December 2009 that was claimed by Yemen's al Qaeda wing and who is thought to be in southern Yemen.
"Asiri is believed to be hiding and moving with senior al Qaeda elements such as (Yemen al Qaeda leader) Nasser al-Wahayshi. Security intelligence are still tracking them down to exactly identify their whereabouts," the official said.
"The campaign includes intensive intelligence and military work," he added. Security forces had been deployed to parts of the two provinces, and were working to seal off some areas.
Maarib and Shabwa are provinces that are known for their impenetrable deserts. Shabwa is in central Yemen and borders the Arabian Sea, while Maarib lies to the west of the country.
The two parcel bombs were intercepted last week on cargo planes in Britain and Dubai and are thought to be the work of al Qaeda's Yemen-based arm, al Qaeda in the Arabian Peninsula (AQAP), US officials say.
The US Treasury has blacklisted Awlaki as a "specially designated global terrorist." Earlier this year, the United States authorized the CIA to capture or kill him.
Last week's plot deepened Western security fears focused on Yemen after AQAP claimed responsibility for a suicide bomb that Saudi Arabia's security chief narrowly survived in August 2009 and a foiled Christmas Day attack on a US-bound plane.
President Barack Obama has increased funding for Yemen this year, providing $150 million in military assistance alone.
Unmanned American drone aircraft gather information about militants and have occasionally fired missiles at them, although neither Washington nor Sanaa is keen to admit this.
Joint US-Yemeni security operations in the past year have failed to kill or capture AQAP's top leadership.
The muscular approach risks provoking a fierce backlash among Yemenis already deeply hostile to the US invasions of Iraq and Afghanistan and to Washington's support for Israel.
Possible "dry run"
In a fresh development in the interception of the bombs, US media said that American intelligence officials tracked several shipments of household goods from Yemen to Chicago in September and considered that the parcels might be a dry run for a militant attack.
Intelligence officials believe the tracking of the shipments may have been used to plan the route and timing for two parcel bombs discovered on US-bound planes in Dubai and London.
The "dry run" involved a carton of household goods including books, religious literature, and a computer disk, but no explosives, shipped from Yemen to Chicago, the report said.
The bombs were hidden in printer toner cartridges and would have been powerful enough to destroy the planes carrying them, Britain said.
The New York Times said the apparent test run may have allowed plotters to estimate when planes carrying the explosive toner cartridges would be over Chicago or another city.
That would permit them to set timers on the two devices to trigger explosions where they would cause the greatest damage, the Times said.
Governments have tightened aviation security after the devices sent in air cargo from Yemen were intercepted.
International airlines body IATA warned on Tuesday against rash moves to improve aviation security.
"We have seen many cases where (solutions) have unintended consequences," Giovanni Bisignani, Director General of the International Air Transport Association (IATA), said at an aviation security conference in Frankfurt.
"Security cannot bring business to a standstill," John Pistole, head of the US Transportation Security Administration, told the conference.
"We must strike that balance (between security and business). The US government understands this well. Protecting freedom of movement is at the heart of our mission."