Bahrain king declares state of emergency after protests
It comes a day after troops from neighbouring Gulf states were sent to Bahrain to help deal with the unrest.
Protesters have blocked all roads leading to the capital's financial centre, the scene of clashes on Sunday that left more than 200 people wounded.
At least two people have been killed in Tuesday's clashes, reports say.
One is reported to be a member of the Bahraini security forces killed in clashes with thousands of protesters in Maamee, state television and the information ministry said.
Another Bahraini was also killed in clashes in nearby Sitra, reports said.
A Bahraini doctor who was at the accident and emergency department at one hospital told the BBC that there were "many, many casualties".
"People are coming in with bullet wounds and injuries caused by rubber bullets. There are hundreds of people," he said. "We received one major case - a man whose skull had been split open by something."
Two other men were in a serious condition after being shot in the eyes, while a third had been shot in the back of the head, the doctor said.
"We were at the health centre in Sitra, and they shot at us. The doctors and nurses were all scared because the windows were being broken and we could hear the shooting. This is a disaster," he added.
He said police and soldiers - both Bahraini and foreign - had seized six ambulances, and then used them to attack protesters.
"The paramedics were kicked out, and they took the ambulances. They went everywhere in them and they were shooting people."
Read More: BBC