JEDDAH - A suicide bomber failed in his attempt to kill the prince who heads Saudi Arabia's anti-terrorism campaign, the first attack on a member of the royal family since the start of a wave of violence by al Qaeda six years ago.

Prince Mohammed bin Nayef, the deputy interior minister and son of the man thought likely to be the next crown prince, was meeting well-wishers on Thursday when a man blew himself up, a ministry spokesman said. The prince was not seriously hurt.

The attack indicates that the threat is out there waiting to happen -- sometimes at closer range than you would think, said one Western diplomat in Saudi, who declined to be named.

The royals will have plenty of reasons to worry in a country where weapons apparently find easy entry from porous borders to the north from Iraq or the south from Yemen.

As security chief, Prince Mohammed is one of the most powerful men in the kingdom and is credited with the government's success in crushing the violence.

Saudi Arabia, the world's largest petroleum exporter and a key U.S. ally in the Middle East, was forced to confront its own role in rising militancy at home and abroad when its nationals turned out to be behind the September 11 attacks on the United States.

The mastermind of those attacks, al Qaeda leader Osama bin Laden, was born in Saudi Arabia.

Al Qaeda in the Arabian Peninsula, the Saudi arm of the group, claimed responsibility for Thursday's bombing attempt, according to a message posted on Islamist internet forums and translated by SITE Intelligence Group.

Interior ministry spokesman Mansour al-Turki said security measures would not be increased after the apparent breach, which occurred after the prince ordered guards not to search the militant, who had insisted he was giving himself up.

The security will not be heightened more than it is at the moment. We have always been saying that we expect (such acts) and act as though they may happen at any moment.

HOME TO ROOST

Royals in Saudi Arabia are obliged to receive visitors during the Muslim fasting month of Ramadan.

The Saudi official news agency said the bomber, whom it did not name, was the only casualty. The attack took place in Prince Mohammed's private office in the Red Sea port of Jeddah.

The incident serves to underscore the possibility of attacks in the kingdom itself. Saudi officials have expressed concern that neighboring Yemen, embroiled in a conflict that has claimed hundreds of lives, could become a staging ground.

Saudi officials worry that militants returning from wars in Iraq or Afghanistan or slipping across the porous border to Yemen may bring with them fighting experience and tactical knowledge of weapons or explosives.

A diplomat from an Arab country, who declined to be named, said the attack, which follows three years of arrests and weapons and explosives seizures, signals that militant networks may extend further than previously thought.
The authorities have always been breaking up new cells with militants that have not been on their radar screen which shows that the country's continues to be a breeding ground for militancy, he said.

What is new is the fact that it targeted a royal, not anyone, but literally the kingdom's security tsar.

Al Arabiya television showed Prince Mohammed, apparently slightly injured, meeting King Abdullah after the attack.

This will only increase our determination to eradicate this (militancy), said Prince Mohammed, who is the son of Interior Minister Prince Nayef bin Abdul-Aziz, recently named second deputy crown prince.

Earlier this month, Saudi authorities announced the arrest of 44 militants close to al Qaeda and the seizure of explosives, detonators and firearms.

Human Rights Watch has criticized the country for detaining thousands without charge while Amnesty International said the state had committed human rights violations on a shocking scale as part of its anti-terrorism drive.

Some analysts say more militant action is likely.

Al Qaeda in the Arabian Peninsula is like a balloon. You squeeze it on one side and it bulges out on the other, said one Gulf-based security analyst who declined to be named.

It's a comeback by al Qaeda trying to find new foothold for itself in Saudi Arabia. We'll see more operations of this kind.

Neighboring Yemen, a poor state of some 23 million people on the tip of the Arabian Peninsula, is battling al Qaeda militants and secessionist discontent in the south, as well as the rebellion in the mountainous north bordering Saudi Arabia.

(Reporting by Souhail Karam in Riyadh with additional reporting by John Irish and Thomas Atkins in Dubai; editing by Angus MacSwan)