Bahrain, which has been the scene of almost daily protests against the Al Khalifa regime since an uprising began in 2011, has been repeatedly criticized by international human rights organizations for torturing prisoners and its excessive use of force against peaceful protesters and those who demand reforms.
Scores of people have been killed in the crackdown and security forces have arrested hundreds including doctors and nurses. Dozens of demonstrators have also been sentenced to jail terms for attending street protests.
Kerry, who is in Manama to prepare for a summit between US President Barack Obama and Persian Gulf heads of state in Saudi Arabia later this month, added that he did not know what type of weapons were used in an airstrike in Yemen that killed 97 civilians, Reuters reorted.
"I don't have any solid information, any documentation with respect to what weapon might or might not have been used. There are questions being asked," Kerry said. "Whatever weapons are being used, our preference is that all shooting stops."
Yemen has been under military attacks by Saudi Arabia and its allies since March 2015.
The death toll from the Saudi-led war so far has reached more than 8000 people. More than half of the total population of Yemen, some 14.4 million people, are also food insecure due to ongoing conflict and import restrictions, according to the Food and Agriculture Organization (FAO).