By Farishta Saeed
MANAMA (Reuters) - A small explosion was heard in the center of the Bahraini capital Manama on Sunday, three witnesses said, as the kingdom was hosting a Formula One motor racing Grand Prix, but the cause was not immediately clear.
Police blocked off the road where the incident took place near a government security building in the bustling Adliya district, where many foreigners live. A security source at the scene said a car had been damaged by fire. The source did not elaborate and there were no reports of casualties.
Small bomb blasts occur sporadically in the U.S.-allied kingdom, which has witnessed low-level political unrest since 2011, when protests mainly by the Shi'ite Muslim community erupted to demand democratic reforms in the Sunni-led government.
But unrest in the run-up to the race, staged about 30 km (20 miles) south of Manama at the Sakhir desert circuit, was markedly lower than in the past two years, apparently due to a more effective security clampdown on Shi'ite villages.
The government sees the Bahrain Grand Prix as a way to raise Bahrain's international profile and attract tourists and foreign investment.
In 2011, when the unrest first broke out as part of the Arab Spring, the race had to be canceled.
Many Bahraini Shi'ites complain of discrimination, especially in employment and housing, a charge that the government denies.
Political reconciliation talks between the government and opposition have made little progress.
Earlier on Sunday, a small crowd of youths in the Shi'ite village of al-Eker, south of Manama, burned tyres and threw stones at police who responded by firing tear gas, Reuters witnesses said. The youths quickly dispersed.
Bahraini activists reported similar sporadic unrest in other areas where dozens of protesters marched inside villages and others threw stones at police who seemed to effectively block off the main entrances to the villages. Reuters could not immediately verify these accounts.
On Friday, tens of thousands of mainly Shi'ite protesters had marched for democratic reforms and on Thursday, anti-government demonstrators throwing petrol bombs clashed with police who fired tear gas and birdshot following a funeral procession in al-Eker.
Meanwhile, police have increasingly come under attack in recent months from home-made bombs and dozens of Bahrainis have been sentenced to prison terms ranging up to life in jail for attacking police stations and attempting to kill policemen.
One of three blasts last month killed three policemen, including one from the UAE. Bahrain quelled the uprising in 2011 with help from forces from its Sunni Gulf Arab allies, Saudi Arabia and the United Arab Emirates.
(Writing by Yara Bayoumy; Editing by Sami Aboudi and Kevin Liffey)