Three demonstrators were killed early on Thursday during police attacks on protesters who continued pushing the government of Bahrain for reform.
The dead included an elderly man aged 60-70 and a young man, whose bodies were at the Salamynia Medial Hospital. Their bodies bore what appeared to be gunshot wounds, witnesses said.
The body of the third victim was still at the location of the protests, where medical staff who rushed to the scene and witnesses confirmed the death to DPA.
The deaths bring to five the number of protesters killed this week during demonstrations in Bahrain triggered by the ouster of former president Hosni Mubarak from Egypt late last week after 18 days of protests.
At least 45 people were being treated at the Manama hospital for injuries caused by teargas and shotgun fire, medical sources said.
Police surrounded the square and opened fire without warning about 3am (0000 GMT), witnesses told DPA.
The crowd of thousands -- estimates range from 5,000 to 20,000 -- included many women and children who joined the demonstrations which had run peacefully through the day following the funeral Wednesday for an earlier victim.
Parents carried children on their shoulders and smiled and waved well into the early hours of Thursday amidst the throngs of protesters, according to televised images shown by Al Jazeera.
One witness told the broadcaster that many in the crowd had settled down to sleep and occupy the square for the duration of the night when they were roused by the police attack.
In the ensuing hours, everyone fled the scene and police took control of the square.
Angry crowds in the meantime had showed up at the hospital, adding to a chaotic scene of shouting and screaming by hundreds of panicked people either seeking medical aid or searching for loved ones.
Earlier Wednesday, a relaxed atmosphere surrounded demonstrations as thousands turned out for the funeral procession carrying Fadel al-Matrook, 31, to the cemetery. He was one of the two demonstrators killed in clashes with security forces in the protests which began Sunday evening.
Some of the marchers shouted "down with the regime" during the funeral, the accounts said.
But most opposition protesters who had taken part in the demos earlier in the week insisted that their demand was for reforms, not regime change.
The funeral march came a day after king of Bahrain Sheikh Hamad bin Isa al-Khalifa set up a special committee to investigate the cause of three days of protests and the violence leading to the two deaths. The king called the deaths regrettable.
Sheikh Hamad was seen as pursuing a course of offering both dialogue as well as using police to curb demonstrations.
Most of the opposition demonstrators are Shias while the ruling house is Sunni.