The ruling is the third tough sentence since Sunday and brings to 91 the number of Shias jailed in four days over violence, amid criticism from rights watchdog Amnesty International.
Two of the defendants were in the dock, while the other two remain at large, said the source.
The four were accused of "forming a terrorist group, attempted murder, and (carrying out) bombings," according to the charge sheet.
Prosecutors say they planted two roadside bombs in November last year in Manama's al Adliya district. One bomb exploded near a rubbish bin wounding an Asian worker, while the second one near an electricity generator was defused.
On Sunday, a Bahraini court handed jail terms of up to 15 years to 50 activists, including a prominent Shia Iraqi cleric, convicted of forming a clandestine opposition group.
Amnesty had slammed the ruling against them as appalling and demanded a probe into allegations that some were tortured.
On Monday, a court jailed 37 other Shias for up to 15 years for carrying out "terrorist crimes" in the kingdom.
In August, King Hamad decreed stiffer penalties for "terror acts" in the country rocked by a Shia-led uprising since 2011.
These include a minimum 10-year jail term for an attempted bombing. If casualties result, the sentence can be life imprisonment or death.
Sunni-ruled Bahrain was rocked by Arab Spring-inspired protests led by the kingdom's Shia majority that were crushed in March 2011.
Bahraini Shias continue to demonstrate in villages outside the capital and frequently clash with police.
At least 89 people have been killed since the protests erupted in 2011, according to the International Federation for Human Rights.
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I have lived for few years in Bahrain in the early 80's. I have seen that many shia employees of our company would simply not turn up for work all of a sudden. We all knew that they were picked up by the agencies. Nothing will be heard of them for months and no one will talk about them. A few weeks or few month later some may return back to work and they would be completely different persons. Though they were friendly and jovial with us before they vanished, they will be very quiet and not talk to anyone after they return. No one would aks them where they were and nor will they talk on this. I have heard from few that their prisons are horrible. If anyone is in prison during Ramzan, it is the worst time for them. The prisons have tall walls and the prisoners stay most of the day in the sun, fasting and not sipping even a drop of water. In the evening they are given Kubooz (a sort of dry bread like Nan) to break their fast. Some of what I have heard may be exaggerated, but Shias who are over 55% of the population in Bahrain live in constant fear there. Their secret service will keep constant tabs on the shias. There were many Pakistanis in the police force too. In fact one Pakistani police officer helped me recover my money from a trader there. I had ordered for contact lens and paid in advance. I had told the owner of the shop that I need it by a certain day as I was leaving the country for good. Unfortunately, the shop did not get its consignment in time from overseas and the shop owner refused to return my advance and said that I have to come a week later to pick up my lens. I went to the nearby police station and the Pakistani officer accompanied me to the shop. As soon as the shop owner saw the police officer, he returned my money and neither did the police officer say anything nor did the shop owner. The still remember the face of this Pakistani police officer and thank him for his assistance.
Keeps persecuting the poor Shias in Bahrain. No one cares about their human rights.