CHENNAI: An Indian court on Monday sentenced crew members of a private American ship, including 25 foreigners, to five years in prison for illegal possession of arms in Indian waters in a verdict that could spark diplomatic tension.

The crew, which included foreign nationals from Ukraine, Estonia and six British former soldiers, was arrested from the ‘Seaman Guard Ohio’ in 2013 after they failed to produce papers authorizing them to carry weapons in India’s territorial waters. Ten Indians were also arrested.

The court in India’s southern city of Tuticorn, in Tamil Nadu state, found the crew guilty of violating Indian laws by possessing prohibited arms. It also fined each crew member 3,000 rupees ($45).

“This judgment is totally unfair and a great injustice to the accused,” Arumugaram Ravipandian, a lawyer representing all 35 crew members, told Reuters.

Ravipandian said his clients would seek bail and challenge the verdict in a higher court.

The crew, that spent nine months in prison after the incident, has been out on bail but not allowed to leave India since 2013.

Paul Towers, a former British soldier among those convicted, said the weapons on board their ship were properly registered.

“We are speaking to our consulate ... this is not justice,” said Towers.

The British High Commission in New Delhi said it was providing consular assistance but could not interfere in another country’s judicial process.

“Our staff in India and the UK have been in close contact with all six men since their arrest to provide support to them and their families, including attending court,” it said in a statement.