Moroccan security forces arrested al-Haili - nicknamed 'the Bear' - in early June. Al-Haili is suspected of training recruits in Afghanistan and placing them in overseas cells. After the US-led military assault on Afghanistan, he helped evacuate Al-Qaeda operatives from the country, US officials said.

The arrest followed the detention in Morocco of three Saudi nationals accused of plotting to attack US and British warships in the Strait of Gibraltar. The head of the group, Abd al-Rahim al-Nashiri, who is also accused of involvement in the 2000 bombing of the USS Cole, has not yet been apprehended.

Morocco earlier extradited Zammar, a German of Syrian descent, to Damascus, where it is understood German intelligence officials have had access to him. The German government has played down his alleged role in the Al-Qaeda network, but the US has accused him of actively recruiting members of the organisation, including the chief 11 September hijacker Mohammed Atta, who lived in Hamburg at the same time as Zammar.

The Saudi security forces have also arrested several men suspected of planning terrorist attacks in the kingdom, the Interior Ministry said on 18 June. It was reported that a Sudanese and one Iraqi national were detained along with 11 Saudis in different operations over the past few months. But the kingdom has said it will handle the case itself, and not allow foreign security forces to interrogate the detainees.

The men are reported to have formed two separate cells, one of which - headed by the Sudanese national - is accused of firing a surface-to-air missile at a US aircraft close to the Prince Sultan airbase in May. The man, identified by US officials as Abu Hufiza, fled to Sudan with the complicity of the other cell. He was extradited to the kingdom in mid June.

The group is also accused of smuggling a large quantity of explosive devices from Yemen. The signing of a border treaty between Saudi Arabia and its neighbour last year, and the more recent renewal of armed border patrols, is intended to limit the flow of contraband items - including weapons - between the countries. The province of Asir, on the border with Yemen, was home to several of the hijackers involved in the 11 September attacks on the US, and the tribes of northern Yemen are believed to be sheltering several men accused by Washington of strong connections to Al-Qaeda.