Gunmen who shot dead two security officers in the eastern Saudi Arabian city of Dammam on Tuesday were connected to previous militant attacks in the region, the Interior Ministry said on Thursday.
"The results of investigations show a link between the targeting of the security officers in Dammam and other terrorist attacks in Qatif and Dammam," the ministry said on Twitter.
The perpetrators had been trained abroad, it said.
Two other policemen were shot dead in Dammam in September.
Eastern Province is home to many Shi'ite Muslims, who form a minority in the conservative Sunni Muslim kingdom.
Shi'ite militants angry at what they say is repression of their community have attacked security forces in the Eastern Province in the past.
The Islamic State group, which controls territory in Syria and Iraq, has also claimed attacks on Saudi security forces as well as deadly bombings and shootings that target the kingdom's Shi'ites.