Saudi security forces have arrested a man who figured on a list of 23 wanted people for causing trouble in the mostly-Shiite Qatif district, rights activists and an official said on Monday.
A police squad arrested Hussein Hasan Ali Al-Rabie in the village of Awamiya late on Sunday, said activists who did not wanted to be named.
Interior ministry spokesman General Mansur al-Turki confirmed the arrest of Rabie.
He said in a statement carried by SPA state news agency that Rabie was wounded in a gunfire exchange with security forces who caught him "while selling a large amount of drugs in Awamiya."
Turki did not say if police arrested others involved in buying the drugs, but he said that a policeman was wounded in the clash.
Rabie was fourth on a list of 23 wanted people announced by the interior ministry earlier this year. His arrest reduces the number of those remaining at large to 13, after five others were arrested.
Four others turned themselves in when the list was announced in January and were later released.
The ministry had said those wanted were responsible for the trouble that hit Qatif, in the oil-rich Eastern Province, last year.
The group is accused mainly of "possessing illegal firearms and opening fire on the public and police, in addition to using innocent people as shields," the interior ministry had said at the time.
They were suspected of taking part in "mobs, blocking traffic (and) damaging public and private property" during sporadic confrontations between police and Shiite protesters.
Confrontations have intensified recently between police and protesters from the Sunni-dominated kingdom's marginalised Shiites -- estimated at about two million and mostly concentrated in Eastern Province.
A policeman and an armed protester were killed in clashes in early August, as a security patrol came under heavy gunfire from four armed rioters on motorbike in Qatif, the interior ministry said.
Two Shiite protesters were killed in July, triggering attacks on government buildings in Qatif.
In May, Amnesty International said seven people had been killed and a number of others injured in clashes between the authorities and protesters in the region since November.
Qatif witnessed a spate of demonstrations after an outbreak of violence between Shiite pilgrims and religious police in the Muslim holy city of Medina in February 2011.
The protests escalated when the kingdom led a force of Gulf troops into neighbouring Bahrain the following month to help crush a Shiite-led uprising against the Sunni monarchy.
Rights groups say more than 600 people from Qatif have been arrested since Spring 2011, but most of them were released.