Saudi Arabia has broken up three Al-Qaeda cells totalling 113 militants who were planning to carry out attacks inside the kingdom, including on its vital oil installations, officials said on Wednesday.

One cell consisted of 101 people and two smaller cells were made up of six men each, the interior ministry said.

There were 47 Saudis and 51 Yemenis, a Somali, a Bangladeshi and an Eritrean in the large cell, it said in a statement read out on state television. The two smaller groups were made up of 11 Saudis and a Yemeni.

Arms, ammunition, computers, pre-paid telephone cards, cash and unspecified documents were all seized in the operation.

The large cell was uncovered as the result of an investigation launched after suspected Al-Qaeda militants -- two of them dressed as women -- tried to infiltrate the country last October with explosives.

The two were killed in a shootout at the border and a third was arrested.

The foreigners in the cell were said to have entered the conservative Muslim kingdom under cover as job-seekers or to visit Islam's holiest sites in Mecca and Medina.

Two members of that cell were said to have been preparing suicide attacks, while the others were to have targeted economic and security targets.

Each of the two small cells was operating without knowledge of the other, and both were said to be linked to Yemen-based Al-Qaeda in the Arabian Peninsula (AQAP) and tasked with targeting oil installations.

The ministry did not say where or when the arrests took place.

Saudi-owned Al-Arabiya television, which showed footage of the seized automatic weapons, quoted an interior ministry spokesman as saying the planned attacks on oil installations in eastern Saudi Arabia were imminent.

"The network and the two cells were targeting oil installations in the eastern region and had plans that were about to be carried out," Mansur al-Turki told the Dubai-based Arab satellite television.

However the ministry's own website said the two small cells "were in the initial stages of preparation for attacks on oil and security installations in the eastern region."

Saudi officials say they have thwarted several plots over the past year, rounding up numerous suspects and seizing weapons caches and bomb-making equipment, all linked to Al-Qaeda.

In August, an AQAP militant, pretending to surrender, smuggled a bomb into Deputy Interior Minister Prince Mohammed bin Nayef's palace in an attempt to kill the top security official.

The device, believed to have been hidden in the militant's underpants, exploded very close to the prince but killed only the bomber himself. The prince suffered minor injuries.

Riyadh is especially concerned about the resurgence of AQAP in Yemen, where government crackdowns on the group have been ineffective.

In September, Michael Leiter, director of the US National Counterterrorism Centre, said the group has gained a dangerous foothold in Yemen.

"We have witnessed the reemergence of Al-Qaeda in the Arabian Peninsula, with Yemen as a key battleground and potential regional base of operations from which Al-Qaeda can plan attacks, train recruits and facilitate the movement of operatives," Leiter told a US Senate hearing.

Earlier this month, Saudi King Abdullah said the kingdom is determined to halt extremism.

"In domestic policy, the government continues to expend its efforts to strengthen security," he said in his annual speech to the Shura Council, the country's consultative assembly.

"A special effort has been made to confront the thinking of the group of deviants, extremists and terrorists," the king said in language commonly used by officials to refer to Al-Qaeda.

"The security services have had repeated successes with preventative actions, and will continue their activities to foil the terrorist plots, eradicate the deviant groups, and dry up the sources of terrorism," he said.

- AFP