Saudi Arabia has detained a man accused of firing at German diplomats as they drove through the Eastern Province village of al-Awamiya in January, the kingdom's interior ministry said on Sunday, Reuters reported.
Nobody was hurt in the incident, but the diplomats' car caught fire.
Ministry spokesman Major General Mansour Turki described the incident as a "terrorist attack" and said that several other suspects had been identified but not detained.
The investigation has also led to the detention of another man wanted in a different case, he said in a statement carried by the official Saudi Press Agency.
Awamiya, a village in the Qatif district of the Eastern Province, has been a focal point for protests against the Saudi government and ruling family, as well as occasional attacks on security forces and police raids to detain activists.
Qatif is mostly inhabited by members of the Shi'ite Muslim minority, who complain they face systematic discrimination from the authorities, which the government denies.
Around 20 people have been killed in Qatif, mainly in Awamiya, since demonstrations started there during the Arab uprisings in 2011.
The government has described all the deaths as resulting from exchanges of fire after gunmen shot at police.
Local activists have accused the authorities of also shooting unarmed protesters during demonstrations and of killing people while attempting to arrest security suspects.
The government denies this. It has said some protests and attacks by Shi'ite demonstrators were instigated by Riyadh's main regional rival Iran, but local activists say this is not true.