Some private companies from Iran, the United Arab Emirates and other Middle Eastern countries were found to have been operating North Korean flag vessels in violation of the latest U.N. Security Council resolution, news reports said Tuesday.

At least four ships -- including the Deniz, the Yekta and the Al Iman -- had been reflagged to the communist country since last year and making port calls at Iran, Iraq and Somalia in care of Iranian and UAE firms, Japan’s Kyodo News and the U.S.’ Voice of America reported.

Resolution 2270, imposed in March in response to Pyongyang’s nuclear and missile tests earlier this year, bans U.N. member states as well as their individuals and entities from registering vessels in the North and obtaining authorization for vessels to use their respective flag.

As of Tuesday evening, the location of the Deniz was last recorded at around 6 p.m. on Sunday near Iran’s Bushehr port along the Persian Gulf, according to an analysis of the Marine Traffic vessel tracking website by The Korea Herald.

The Yekta was last positioned in waters off the Iran-Iraq border at the tip of the gulf on April 27, while the Al Iman was seen on May 8 cruising the Red Sea between Saudi Arabia and Sudan.

Through the use of the flag of convenience ships, the cash-strapped communist regime could likely be earning foreign currency, while the owner companies benefit from relatively low registration fees and related taxes, Kyodo noted.

Claudia Rosett, a foreign affairs columnist for Forbes.com, claimed late last month that the Yekta is registered in Dubai alongside another North Korean flagged ship the Shaima, whereas the Deniz has since February 2015 been owned by Siri Maritime Services in Tehran, citing Lloyd’s and Equasis maritime databases and International Maritime Organization’s shipping line records. They were renamed and reflagged to North Korea within the past 18 months.

While no signs of any wrongdoing have been detected, she raised concerns about a possible loophole in the latest sanctions that blacklisted only 27. There are more than 100 other active North Korean flag ships, and some have records of being caught while clandestinely carrying weapons and other illicit items, she noted.

In another development, at least four of the 27, most of which had returned home after being denied entry to overseas ports in early March in line with the newest sanctions, have reappeared sailing in waters outside North Korea over the past several weeks, Marine Traffic data showed.

The Mi Rim 2, the Chong Chon Gang and the Greenlight apparently turned up off the coast of Japan on May 14, May 3 and April 5, respectively, as well as the Se Pho near the eastern coastal Chinese province of Shandong in the West Sea on May 7.

Seoul’s Foreign Ministry has said it is closely monitoring related movements and continuing diplomatic efforts to ensure a thorough implement of the UNSC sanctions.

By Shin Hyon-hee (heeshin@heraldcorp.com)