ISTANBUL Ñ Turkey has deployed its navy and coast guard to secure the NATO summit.

The summit, which formally began on Monday, was launched amid threats by Al Qaida-aligned groups to attack Western leaders. Last week, bombs were detonated in Ankara and Istanbul in what was described as attacks by Ansar Al Islam, Middle East Newsline reported.

Officials said Turkey has deployed dozens of naval and coast guard vessels in an effort to keep all suspicious boats out of the Bosphorus. They said the naval vessels, backed by F-16 multi-role fighters, have patrolled the Bosphorus between the European and Asian sides of the city.

On Saturday, officials said, Turkey closed both the Bosphorus and the Dardanelles to ships carrying explosives, weapons and oil. The closure was meant to last until late Tuesday after the 49 world leaders, including U.S. President George Bush, leave Turkey.

Officials said the Bosphorus Strait has also been under constant surveillance. They said cameras and infrared sensors were deployed along the waterway to provide 24 hour a day coverage until June 30. Turkey has been helped by the United States in the surveillance effort, the officials said.

NATO has also helped Turkey by deploying three airborne early-warning AWACS aircraft to protect the summit. NATO was also expected to announce training and support for Iraq's new military and security forces. Iraq has asked NATO for equipment, training and technical assistance.

At the same time, Turkey authorities have stepped up arrests of suspected insurgents. Over the weekend, Turkish police detained 10 people suspected of being linked to Al Qaida in the central province of Konya.

Turkish security sources said authorities captured guns, ammunition, a hand grenade and manuals on making bombs. They said the detainees were trained in Afghanistan and Bosnia.