A firefight in a mainly Shiite area of eastern Saudi Arabia killed four people -- two policemen and two people wanted over violence -- on Thursday, the interior ministry said.
The police came under fire when they attempted to arrest the two wanted activists in the flashpoint Awamiya district of the oil-rich Eastern Province, said a ministry statement carried by the official SPA news agency.
The activists, named as Hussein Ali al-Faraj and Ali Ahmed al-Faraj, were both also killed.
Two other police were wounded and required hospital treatment.
Security forces who tried to arrest those suspected of being behind "armed unrest" were shot at and retaliated, a ministry spokesman was quoted as saying.
They seized "two weapons, a large quantity of ammunition, a bulletproof vest and weapons sights," he added, warning the authorities would crush any such resistance with "an iron fist".
Awamiya has continued to experience problems despite the end of mass protests that erupted in the eastern region in March 2011 in the wake of the Arab Spring.
In January, the US embassy in Riyadh warned its citizens against travelling to the district after gunmen attacked the car of two German diplomats.
Demonstrations in Eastern Province, where most of the kingdom's two million Shiites live, erupted simultaneously with a protest movement in neighbouring Bahrain in 2011.
They took a violent turn in 2012 and clashes between police and protesters have so far killed 24 people, including at least four policemen, according to activists.
Of more than 950 people arrested since 2011 for involvement in the unrest in the province, 217 are still being held.
The clash came a day after a Saudi court jailed seven protesters for up to 20 years for joining a demonstration and chanting anti-government slogans in the Eastern Province.