MOMBASA, Kenya (Reuters)—A Kenyan court sentenced seven Somalis to 20 years in jail for piracy on Wednesday, a boost to international efforts to drive out pirates from the waters off the Horn of Africa nation.

Despite the presence of several foreign navies off the coast of Somalia, pirates have continued to seize vessels and to rake in millions of dollars in ransom payments, driving up the cost of shipping insurance.

The seven were captured by Danish naval forces after they attempted to hijack a Sri Lankan fishing trawler off the Gulf of Aden. They were handed over to Kenyan authorities, who have held them since October 2009.

In her ruling, Magistrate Joyce Gandani said piracy had been on the increase, and the long jail sentence should serve as a deterrent to others.

"The acts of piracy have adversely affected the security and the trade of not only our country, but the entire region," she said.

Barre Ali Farah, Abdi Mohammed, Ali Hussein Hassan, Abdulkarim Nur Shire, Bashir Mohammed Ehmi, Abdulrazak Abdullahi Ali and Abdulfaruk Hussein Ali sat pensively in the crowded courtroom as Magistrate Gandani read them their sentence through an interpreter.

Their lawyer, Jared Magolo, said the sentence was harsh because the court had not taken into account the years the defendants had already spent in custody. He vowed to appeal.

"This is child's play compared to other cases where the alleged pirates exchanged fire using automatic rifles and injured the crew," he told reporters, adding that his clients were only armed with knives when they were captured.

The first batch of seven Somali pirates to be tried in Kenya were sentenced to five years each in 2006.

The U.N. Monitoring Group on Somalia said in a recent report to the Security Council, seen by Reuters, that senior pirate leaders were benefiting from high level protection from Somali authorities and were not being sufficiently targeted for arrest or sanction by international authorities.

Kenya sent troops into neighboring Somalia in pursuit of al Shabaab rebels last year, drawing a series of retaliatory attacks on its soil.