Jordanian authorities have foiled an al Qaeda plot targeting shopping malls and Western diplomats, according to reports.
Sameeh Maaytah, a spokesman for the Jordanian government, said 11 suspected militants were in police custody.
State news agency Petra said they were planning a wave of attacks on diplomatic missions, hotels and other key sites.
Mr Maaytah said the men - who are all Jordanian citizens - had brought arms into Jordan from neighbouring Syria to use in the alleged plot.
"The kind of weapons, explosives, they were ready to use include mortars and machine guns," he said.
"I say again they hold Jordanian nationality, they went to Syria and came back using the Samr route which crosses the Syrian-Jordanian border."
He added that al Qaeda operatives based in Iraq have been assisting the suspects with the manufacture of explosives.
The suspects were arrested over the past few days by Jordanian intelligence agents, he said.
A judicial source told AFP that the case had been referred to the prosecutor of the state security court - a military tribunal.
"They will face two charges: conspiracy to carry out terrorist acts and possession of explosives," said the source who declined to be named. The charges carry the death penalty.
The group scouted possible targets in Amman, experimented with explosives after getting hold of raw materials to make bombs, and had begun selecting possible suicide bomb candidates, Petra said.
Among their alleged plans were attacks on two malls as well as a major attack in the upmarket Abdoun neighbourhood in western Amman.
A security source told Reuters the cell had manufactured explosives "aimed at inflicting the heaviest losses possible".
"The group was able to devise new types of explosives to be used for the first time and planned to add TNT to increase their destructive impact," the source said.
Jordan is a key US ally and is one of the safest countries in the Middle East. However, it has seen al Qaeda-linked violence before.
In 2005, triple suicide bomb attacks at luxury hotels in the capital Amman killed 60 people.
Sunday's announcement that attacks have been foiled comes days after several reports that Jordanian authorities have arrested jihadists in recent months who cross into Syria to join the anti-regime armed insurgency there.