Police in Saudi Arabia have arrested 88 men - half of whom are Saudis - and are suspected to be part of an al-Qaida terrorist cell operating in the kingdom.
Interior Ministry spokesman Mansour al-Turki said a number of the suspects had previously been detained on similar charges, but were released.
An Interior Ministry statement said the ministry had been following a number of suspects in view of what it called the spread of "strife and sick ideas" that lured members of the community to "places of strife".
Some of the suspects had links to the Islamic State group operating in Syria and Iraq, to the Nusra Front group in Syria or to the al Qaida branch in Yemen, Ministry spokesman Major General Mansour Turki told Reuters after a news conference.
"They showed their support to the organizations in Syria and Iraq and also in Yemen, and they wanted to get involved in their activities. Some of them tried to get ... instructions of what he should do, how he should act inside the kingdom," said Turki.
He said those who were in contact with militant groups overseas may not have also been in contact with each other.
Turki told the news conference that 48 of those arrested were Saudis and many had been planning assassinations.
Saudi Arabia has been battling al-Qaida for more than a decade, since militants threatened the monarchy.
The likely targets for assassination were government security officials, Turki said, but might also include clerics who argued against militant ideology.
Turki said that around 2,500 Saudis were believed to be involved in militant activities abroad, including in Syria, Iraq, Yemen and Afghanistan.
He added that since King Abdullah in February decreed long prison terms for any who went abroad to fight, around 300 Saudis had been detained after returning to the kingdom from Syria and Iraq or being caught planning to travel there.
Riyadh has long expressed fears of being targeted by Islamist jihadists, including by some of its own citizens, who have taken part in insurgencies in Iraq and Syria.
King's warning to extremists
King Abdullah said over the weekend that countries ignored terrorism at their own risk, and warned that extremists could once again attack the United States and Europe.
Most of those arrested were Saudi nationals, and at least three were from Yemen.
Officials said security forces had been tracking the men for months.
Al-Qaida founder Osama bin Laden, who was killed in a U.S. raid, was a Saudi national whose family originated from Yemen.
Some information for this report provided by Reuters