A bomb exploded in the lobby of a luxury seafront hotel in Bahrain on Sunday, injuring at least four people. An Islamic organization claimed responsibility for the attack.

The blast followed weeks of anti-government unrest in the Persian Gulf island state, a financial hub in the region and a key U.S. Navy base.A government source, speaking on condition of anonymity, said a bomb exploded at 9 p.m. (11 a.m. MST) at the 15-story downtown Diplomat Hotel, which overlooks the gulf.

Two security sources, who also spoke on condition of anonymity, said at least four people were injured and that the bomb was placed in the lobby, between the reception desk and the elevators.

Witnesses said several employees of the hotel were rushed to hospitals in ambulances. A Pentagon spokesman said he had no reports of American casualties.

A man claiming to speak for the Islamic Front for the Liberation of Bahrain, the most militant of the groups opposing the government, claimed responsibility for the blast in a telephone call to The Associated Press.

"We put a bomb in the Diplomat Hotel 20 minutes ago," the man said, speaking in Arabic-accented English. "Tell the government, which has arrested 2,000 people, that after the feast, we will destroy every place."

He was referring to the three-day feast ending the current Muslim holy fasting month of Ramadan. The feast begins Feb. 19 or 20, depending on the sighting of the crescent moon.

Guests at the Diplomat said they heard a deafening blast, then were showered with glass and ceiling tiles as the lobby filled with smoke.

An 42-year-old Indian businessman who was in the hotel restaurant, just off the lobby, said the explosion was close to where he had been sitting.

"If I hadn't moved to the salad bar, I'd have had it," he told The Associated Press. He declined to give his name.

Guests streamed out of the hotel, crying and hugging each other.

Carol Mason, an American guest, said she and her husband just "grabbed our luggage and ran" as the lobby filled with smoke.

"This was our last day here, and we carry sweet memories of this country, though the bad one will always remain with us," she said.

Her husband Gerald, 42, works at the state-run Saudi Aramco oil company in neighboring Saudi Arabia. They would not give their hometown.

Police have arrested hundreds of people in the current wave of unrest that flared in January. On Jan. 17, a small bomb exploded in a ground-floor toilet at the plush Royal Meridien Hotel, but there were no casualties.

Opposition leaders say the protesters want the restoration of parliament, suspended in 1975 for criticizing the government, freedom of speech, more job opportunities and the release of all political prisoners.

Bahraini authorities accuse Iran of inciting the violence, which has largely involved the emirate's Shiite Muslim majority. Iran, whose population is overwhelmingly Shiite, denies that.

The Islamic Front for the Liberation of Bahrain, a Shiite group, is the only one of the opposition groups that regularly calls for the overthrow of the royal family. Believed to be Iranian-backed, it regularly issues statements from its offices in London and Beirut that lambast the ruling Al Khalifa dynasty.

A more moderate Shiite group, the London-based Bahrain Freedom Movement, condemned the latest attack. It said in a statement that "we firmly believe in peaceful solutions for the political crisis in Bahrain."

Bahrain's Shiites comprise just over half the state's 500,000 citizens. The Al Khalifa family belong to the mainstream Sunni sect of Islam.

The Bahraini government source said the bomb was "locally made," meaning authorities did not think it had been brought in from outside.