Western security sources have told The Daily Telegraph that attacks on football fans watching the World Cup final in Uganda had been carried out by "Al-Qaeda in East Africa," rather than the Somali group al-Shabaab which claimed responsibility.

US officials have talked recently of an increase of al-Qaeda activity in East Africa where militants have been helping train al-Shabaab fighters.

Al-Shabaab has claimed allegiance to al-Qaeda but its ability to launch attacks outside the country had been limited until the Kampala attacks in July. The group has recently been involved in heavy fighting in the Somali capital Mogadishu.

Last night Dutch security officials were continuing to question a British man of Somali origin who was arrested on a plane at Schiphol airport on his way from Liverpool to Entebbe.

Dutch prosecutors said they were investigating the man for links to a terrorist organisation but had not found any explosives.

A European diplomat in Kampala, Uganda's capital, said the man arrested in Amsterdam could have been acting as a copycat after the publicity following the Ugandan attack, which was blamed on the presence of Ugandan troops in Somalia under an African Union peace keeping mandate.