SANAA (Reuters) - Two suicide car bombers set off a series of explosions outside the heavily fortified U.S. embassy in Yemen on Wednesday, killing 16 people, a Yemeni Interior Ministry official said.

The U.S. State Department said the bombings bore “all the hallmarks” of an al Qaeda attack but the United States had not yet concluded who was to blame.

Islamic Jihad in Yemen, a group some Yemeni analysts say is linked to al Qaeda, claimed responsibility for the attack, in which other militants armed with assault rifles and rocket propelled grenades tried to storm the embassy.

“We, the organization of Islamic Jihad in Yemen declare our responsibility for the suicide attack on the American embassy in Sanaa,” Islamic Jihad said in a statement, adding it will carry out more attacks in the future.

Among the dead were six attackers and four bystanders. The rest were Yemeni security personnel, including one embassy guard. All the dead were Yemeni, with the exception of one Indian woman who was walking past when the attack happened, the official added.

In Washington, State Department spokesman Gordon Duguid said all the embassy staff were safe. The embassy and its consular section were closed following the attack.

U.S. President George W. Bush said the attackers were trying to make the United States “lose our nerve and to withdraw from regions of the world.”

“This attack is a reminder that we are at war with extremists who will murder innocent people to achieve their ideological objectives,” said Bush, with the outgoing U.S. commander in Iraq, Gen. David Petraeus, at his side.

When asked which group was suspected in the attack, State Department spokesman Sean McCormack said: “After talking to the security personnel, the attack bears all the hallmarks of an al Qaeda attack where you have multiple vehicle-borne devices.”

Some Yemeni analysts say Islamic Jihad, which is unrelated to a Palestinian group with the same name, is linked to al Qaeda but this has not been clearly shown to be the case.

TRYING TO STORM EMBASSY

Details of the assault remained hazy. But the Yemeni Interior Ministry official said the suicide attackers had tried to break through the heavily guarded gates of the embassy with their cars but had failed, and that the building was not seriously damaged.

McCormack said that one car bomb exploded at a guard’s post outside the embassy and the second near a pedestrian entrance. Several attackers were seen on foot and the goal appeared to be to breach the wall of the embassy complex and to kill people inside.

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Yemen, the ancestral home of al Qaeda leader Osama bin Laden, has grappled with a spate of al Qaeda attacks this year, including one on the U.S. embassy, another near the Italian mission and others on Western tourists.

Islamic Jihad in Yemen has been involved in previous attacks on Western targets in Yemen including a U.S. hospital.

The leader of the group was executed in 1999 for the kidnapping of 16 Western tourists, four of whom died in a botched army attack to free them.

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It had threatened on Tuesday to launch a series of attacks unless Yemen freed several jailed members.

An al Qaeda-affiliated group claimed responsibility in March for a mortar attack that missed the U.S. embassy but wounded 13 girls at a nearby school.

The United States ordered non-essential staff to leave Yemen in April after an attack on a residential compound.

The Yemeni government joined the U.S.-led war against terrorism following the September 11 attacks on U.S. cities in 2001.

It has jailed dozens of militants in connection with bombings of Western targets and clashes with authorities, but is still viewed in the West as a haven for Islamist militants.

Over a third of the more than 250 prisoners at the U.S. prison for terrorism suspects at Guantanamo Bay are from Yemen.

The government of the poor Arab country has also been fighting Shi’ite rebels in the northern province of Saada since 2004 and faced protests against unemployment and inflation.