Image copyright AFP Image caption Senat is accused of having helped North Korea's Chong Chon Gang vessel in smuggling arms

The US has blacklisted a Singapore-based shipping firm over allegations it is supporting illicit arms shipments to North Korea.

The US Treasury said that Senat Shipping was providing "extensive support" to a North Korean company already under sanctions.

It means that any assets the firm holds in the US are frozen and prohibits US citizens from doing business with it.

Senat Shipping has denied the allegations.

The US Treasury makes clear that measures against Senat Shipping also extend to the company's president, Leonard Lai.

It said that Senat Shipping was co-operating with Ocean Maritime Management Company (OMMC), a North Korean firm already under sanctions.

In 2013, a ship operated by OMMC was seized by Panamanian authorities for hiding undeclared military equipment from Cuba under its cargo of sugar.

According to US authorities, Senat arranged the purchase, repair, certification, and crewing of vessels for OMMC.

Image copyright AP Image caption The ship that docked in Panama in 2013 was found to have military equipment - and was operated by OMMC

"Arms shipments transported by OMMC serve as a key resource for North Korea's ongoing proliferation activities," said a US Treasury press release.

The United Nations and the US imposed sanctions on OMMC in July 2014 for the attempted arms import into North Korea.

Senat Shipping's statement confirmed that it had chartered OMMC vessels in the past to operate part of its business but says since then it had stopped dealing with all North Korean ship owners.

The firm denies all of the accusations brought against it by the US.

Company president Leonard Lai said the US move to put him and his company on the blacklist was "purely based on my historical dealings with OMMC and not based on anything illegal".

Under UN sanctions, North Korea is banned from weapons exports and the import of all but small arms. There are also separate US sanctions also target Pyongyang's nuclear arms programme.