(Adds details on EU Commission)

BRUSSELS, Nov 5 (Reuters) - Al Qaeda remains the major security threat to the European Union and a fresh attack by Islamist militants is likely, the bloc's new anti-terrorism chief said on Monday.

"An attack perpetrated by local or international networks remains likely," Gilles de Kerchove, appointed in September to coordinate member states' counter-terrorism policies, told EU lawmakers.

"Al Qaeda ... continues to be the most serious terrorism threat to Europe," de Kerchove told the European Parliament's justice, liberty and security committee.

He said the movement founded by Saudi-born militant Osama bin Laden, who inspired the Sept. 11, 2001 attacks on the United States, had also inspired local radicals.

The EU's executive Commission is due to say on Tuesday that EU states must collect data on air travellers and crack down on militant Web sites to better fight terrorism.

De Kerchove, a Belgian official, said many EU countries were particularly concerned by attacks in North Africa.

Al Qaeda in the Islamic Maghreb grew out of the Salafist Group for Preaching and Combat (GSPC) in January, after winning approval from bin Laden to rename itself an al Qaeda affiliate.

Since then, the Islamists have launched a wave of attacks targeting Algerian security and Western interests.

"The fact that it has embraced Al Qaeda's international terrorism, and the Maghreb's geographical proximity to Europe brings terrorism closer to the borders of Europe," de Kerchove said.

Conflicts in Iraq and Afghanistan had "a considerable impact on radicalisation of extremists in Europe", he added.

Attack plots with suspected ties to Al Qaeda were foiled in Germany and Denmark in September.

An attack by British Islamist killed 52 people on July 7, 2005 on London's transport network.

Prosecutors say the March 2004 attack on Madrid, which killed 191 people, was carried out by a group linked to Al Qaeda.

(Reporting by Ingrid Melander; Editing by Matthew Tostevin)

AlertNet news is provided by