The US Justice Department said it took possession of the North Korea-registered bulk carrier M/V Wise Honest one year after it was detained in Indonesia.

It said the vessel's owner, the Korea Songi Shipping Company, had used it to illicitly export coal and import heavy machine, and paid for maintenance and equipment using US dollars in violation of US and international sanctions on North Korea.

It was the first time a North Korean cargo vessel had been seized for sanctions violation, after several years of high seas cat-and-mouse games in which Korean shippers disguised vessels, used false flags and turned off their tracking transponders to avoid discovery.

The announcement came as tensions rose over Pyongyang's test launch early Thursday of two suspected short-range missiles, the second such move in a week.

"Our office uncovered North Korea's scheme to export tons of high-grade coal to foreign buyers by concealing the origin of their ship, the Wise Honest," US attorney Geoffrey Berman said in a statement.

"With this seizure, we have significantly disrupted that cycle. We are willing and able to deploy the full array of law enforcement tools to detect, deter and prosecute North Korea's deceptive attempts to evade sanctions," he said.

The United States and the United Nations have led efforts to bring economic pressure on North Korea to curtail its nuclear weapons and long-range missile development programs.

Sanctions have targeted the country's economic lifelines by banning its exports of raw materials like coal and iron, labor and some farm goods, and limiting its imports of oil and other fuels.

In addition, US sanctions have aimed to lock the country out of the international banking system by preventing banks with US arms from dealing with North Korean businesses.

North Korean leader Kim Jong Un has met with President Donald Trump twice since last year to discuss reeling in North Korea's nuclear program in exchange for removing sanctions, but the two sides are at an impasse.

- Ship first detained by Indonesia -

The 17,000 tonne Wise Honest, built in 1989, was detained by Indonesian authorities on April 2, 2018, more than two months before Trump and Kim held their first ice-breaking summit in Singapore.

Loaded down with a $3 million shipment of North Korean coal, the vessel had entered Indonesian waters with its AIS tracking transponder turned off and was operating under two registrations, North Korea and Sierra Leone.

The transponder, officials said, in fact had not been on since August 2017.

The captain was arrested and charged with "knowingly hoisting a false flag," according to UN Security Council documents.

Based on the illicit shipping effort and financing of transactions related to the ship that were put through US banks, a US judge issued a warrant to seize the vessel on July 17, 2018.

Officials announced the seizure Thursday as the vessel was close to entering US territorial waters.

"This sanctions-busting ship is now out of service," said Assistant Attorney General John Demers in a statement.

"North Korea, and the companies that help it evade US and UN sanctions, should know that we will use all tools at our disposal -- including a civil forfeiture action such as this one or criminal charges -- to enforce the sanctions."