Bahrain issued arrest warrants on Wednesday for 20 people in an investigation into home-made bombs that injured policemen combating pro-democracy unrest in the Gulf Arab state. \"The criminal investigations chief announced a list with photos of 20 individuals wanted for terrorist explosions,\" an interior ministry statement said. \"The public prosecution has permitted publishing the images to allow ... speedy arrest(s).\" It said the 20 were suspected of preparing and detonating home-made explosive devices that targeted policemen and injured both security personnel and civilians. The names of the men, aged from 18 to 38, were obtained from questioning of detainees and other evidence. The interior minister called on citizens to help in the arrest of the men by calling a phone number with information. Bahrain has been in turmoil since protesters mainly from the Shi\'ite Muslim majority rose up for democratic reforms in early 2011. More than a year later, protests continue and recently intensified, with daily clashes between police firing tear gas to stop unlicensed marches and youths who throw petrol bombs. Thirty-five people had died when a period of martial law ended last June but the total has risen to 81, the opposition Wefaq party says. The government rejects the figure, saying many died from previous medical conditions. Some died in custody. Police say 15 policemen had been wounded by three homemade bombs since early April. The government said this month it would step up efforts to crackdown on what it calls rioting. The opposition says the ruling Al Khalifa family, which has rejected demands for an elected government in Bahrain, an important US ally against Iran, does not want to cede powers.