Two Bahraini girls were arrested for allegedly having plotted to carry out an attack on Sakhir circuit during the weekend's Formula One Grand Prix race, police said on Tuesday.
Authorities arrested "two girls who were trying to carry out a terrorist act at Bahrain's international circuit in the south, as the kingdom was hosting the Formula One race," state news agency BNA quoted police as saying.
The pair were arrested on Saturday, the second day of practice sessions, at one of the entrances to the Sakhir circuit, south of Manama, said public security chief General Tariq Hassan.
He did not give the age of the girls but said one of them had concealed a pillow under her clothes and explained that this was a dry run "to test security measures."
The pair, identified as Nafisa al-Asfur and Rihanna al-Musawi, are being held for 60 days on charges of seeking to "bomb the Sakhir circuit."
The public security chief said 8,000 policemen had taken part in securing the race, against which thousands of Shiites had demonstrated the previous week.
He said police had seized 1,000 petrol bombs, 137 tyres protesters were planning to set ablaze as well as 72 fire extinguishers which were to be used as bombs.
The race took place without disruption despite the backdrop of daily clashes between protesters and police, in Shiite villages away from Sakhir.
Strategically located just across the Gulf from Iran, Bahrain is home base to the US Navy's Fifth Fleet and is also a major offshore financial and services centre for its Arab neighbours in the oil-rich Gulf.
The Shiite Muslim-majority kingdom, ruled by a Sunni dynasty, was rocked by a month-long uprising in 2011, which was crushed with the help of Gulf troops led by neighbouring Saudi Arabia.
Elsewhere on Tuesday the interior minister of Bahrain, Sheikh Rashid bin Abdullah Al-Khalifa, warned that Arab monarchies of the Gulf are endangered and must stand united.
"The danger facing the countries of the Gulf Cooperation Council concerns each and everyone of us and demands that we be united," he said at a consultative meeting of GCC interior ministers in Manama, the BNA reported.
Bahrain -- which is a member of the GCC along with Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates -- accuses Iran of backing the Shiite-led uprising in the Sunni-ruled kingdom.
Oman was also the site of a brief protest movement in 2011 which quickly subsided and several bloggers are on trial for "defaming" Sultan Qaboos.
The UAE, spared by the unrest, has cracked down on activists calling for reform and is trying 94 Emirati Islamists over their alleged links to the Muslim Brotherhood.
On Thursday the UAE announced it had broken up an Al-Qaeda cell comprising seven Arabs who were plotting attacks in the Gulf state.
An official statement on the official Emirati WAM news agency said the group was also "trying to extend its activities to reach some other countries in the region." It did not elaborate.