Suspects' east African roots may hold clues
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Yasin Hassan Omar was born in Somalia, a country whose previous government collapsed in 1991. Since then, it has been ruled by an anarchic collection of feuding clans, radical Islamist groups and militiamen.
Ever since Somali gunmen killed American soldiers and shot down a Black Hawk helicopter in Mogadishu in 1993, the US has suspected that money and guns for al-Qa'ida flow freely through Somalia. Somalia's long, unpoliced coastline is a haven for smugglers taking goods between sub-Saharan Africa and the Middle East.
It is through Somalia that bombers attacked American embassies in Nairobi and Dar es Salaam in 1998, and a hotel in Mombasa where Israeli tourists were staying in 2002.
Since 2003 a new, more ruthless Islamic radical group has set up in Mogadishu, led by Aden Hashi Ayro, a young militia leader who received training in Afghanistan. This group made its presence felt by murdering four foreign aid workers between October 2003 and April 2004.
The International Crisis Group accepts that the Islamic jihad movement has made little headway in Somalia, considering its long years of civic conflict and statelessness. But the think-tank warns: "If Somalia's protracted crisis is allowed to persist, its stateless territory will continue to attract criminal and extremist elements."
The second London bombing suspect, Muktar Said Ibrahim, also known as Muktar Mohammed Said, comes from Eritrea, a less obvious base for terrorism. Since it gained independence from Ethiopia in 1993, Eritrea has been keen to be perceived as a responsible member of the international community. It is currently part of America's "coalition of the willing", but neighbouring countries have pointed out that several rebel groups, including the Sudan Liberation Army, which fights the Sudanese government in Darfur, have set up training camps within its borders.
The country's contact with radical Islamic movements comes from the Eritrean Islamic Jihad Movement. Eritreans were largely sympathetic to government claims that the movement was a terrorist cell that should be destroyed, but President Isaias Afwerki has since labelled so many of his political opponents terrorists that the term has lost meaning.
Moderate Muslims within Eritrea have also become increasingly radicalised after the government interned Muslim elders without trial for over two years. The Eritrean government, which was once seen as the Horn of Africa's greatest hope of modernisation, has become increasingly paranoid. Journalists are rarely granted access to the country and relations with Ethiopia have disintegrated over a border conflict.