The United States imposed financial sanctions Tuesday against six individuals and several companies linked to arms proliferation by North Korea.

The sanctions targeted North Korea's Strategic Rocket Force, two banks and three shipping companies allegedly involved in the arms trade, according to the US Treasury.

Among the targets was the Tanchon Commercial Bank, the financial arm of the Korea Mining and Development Trading Corporation, which is responsible for North Korea arms exports.

Five of the bank's representatives -- two of whom were based in Syria and two others in Vietnam -- also were hit with sanctions.

Also blacklisted was the North Korean representative in Russia of the Foreign Trade Bank, North Korea's primary foreign exchange bank.

The sanctions bar American citizens or companies from engaging in transactions with the designated individuals and companies, and freezes any US-based assets they may have.

"North Korea threatens international peace and security by expanding its nuclear program and continuing its proliferation of weapons of mass destruction and conventional weapons," said Adam Szubin, acting under secretary for terrorism and financial intelligence.

"Treasury is committed to exposing North Korea's global proliferation network and excluding these facilitators from the international financial system."

In sanctioning North Korea's Strategic Rocket Force, the Treasury noted it had carried out multiple ballistic missile tests in 2014.

The three blacklisted shipping companies were accused of transporting weapons.

S. Korean navy fires warning shots at Chinese patrol boat
Seoul (AFP) Dec 8, 2015 - The South Korean navy fired warning shots Tuesday at a Chinese patrol boat that crossed the disputed maritime border between South and North Korea, military officials in Seoul said.

A statement from the Joint Chiefs of Staff said the action was taken after the initially unidentified vessel encroached on South Korean territorial waters.

"It retreated as the warning shots were being fired," the statement said.

The Defence Ministry said the vessel was initially assumed to be North Korean. Naval patrol boats from the North regularly test the boundaries of the Yellow Sea border which has been a military flashpoint between the two Koreas for decades.

"But it actually turned out to be a Chinese patrol boat cracking down on illegal Chinese fishing vessels," a ministry official told AFP.

Seoul has been asking Beijing to take a tougher stand on Chinese vessels that have been entering South Korean waters in increasing numbers to sate growing demand at home for fresh seafood.

Small, wooden Chinese ships were once tolerated in an area where the top priority has always been guarding against potential incursions from North Korea.

But in recent years, the small boats have given way to larger steel trawlers who engage in bottom trawling - dragging a large, weighted net across the sea floor that sweeps up everything in its path.

Around 2,200 Chinese vessels have been stopped and fined by South Korea for illegal fishing in the past four years, and the number of arrested fishermen jumped from two in 2010 to 66 in 2013.

There have been numerous cases of violent clashes between Chinese crews and South Korean coastguard trying to board their boats.

Pyongyang does not recognise the Yellow Sea border that was unilaterally drawn by US-led UN forces at the end of the 1950-53 Korean War.

The boundary was the scene of deadly naval clashes between the two Koreas in 1999, 2002 and 2009.