"Judge J C Jagdale convicted them for attempt to murder and kidnapping and sentenced them to seven years in prison," said special public prosecutor Ranjeet Sangle.
The Mumbai sessions court also imposed a fine of Rs 6,000 each on them.
It directed the government to deport the convicts to Somalia after they serve their prison terms.
The judge, however, acquitted them of charges of 'kidnapping for ransom' (where the maximum punishment is death) and offences under the Arms Act.
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The Indian Coast Guard received a distress call about piracy attempt from a merchant vessel south of Lakshadweep Islands in January 2011.
The Coast Guard's Dornier aircraft spotted two small pirate skiffs which were approaching the merchant vessel. On seeing the aircraft, the pirates retreated.
Following which, the Indian Navy and the Coast Guard launched a chase, and intercepted Prantalaya 14 on January 28, 2011. The pirates, who had 25 AK-47 assault rifles and two rocket launchers, opened fire on the Navy boat, and when the fire was returned, their mother vessel caught fire.
A case was registered against the remaining pirates at the Yellow Gate police station in Mumbai.
Prosecutor Sangle said he examined 15 witnesses during the trial. However, the rescued Thai and Myanmarese nationals did not depose, which, according to him, led to prosecution's failure to establish the charge of kidnapping for ransom.
The Navy and Coast Guard had nabbed a total of 120 pirates between January and March 2011. The pirates who were convicted today belonged to the first batch of those arrested.
Judgements in remaining cases are awaited. All 119 pirates (one died during the trial) pleaded guilty before the court in Mumbai.