SEOUL, Feb 22 (Reuters) - Chinese banks including a branch of China’s biggest bank Industrial and Commercial Bank of China (ICBC) have frozen accounts belonging to North Koreans, a South Korean newspaper reported on Monday.

Citing phone conversations with an unnamed employee of ICBC’s office in the northeastern Chinese border city of Dandong, the Dong-A Ilbo reported that since late December it had suspended all deposits and transfers of foreign currencies in and out of accounts with North Korean names.

“(The bank) had never told me why it was taking such measures, but it seems that they are related with the strained relations between North Korea and China,” the ICBC employee told the Dong-A Ilbo.

An official with ICBC could not immediately be reached for comment on Monday.

Washington and Seoul are seeking support from Beijing, Pyongyang’s main ally, for tougher sanctions against North Korea for its Feb. 7 rocket launch and January nuclear test.

After the rocket launch, another bank in northeast China, had also blocked transactions to North Koreans’ accounts, according to the Dong-A Ilbo report, which cited a Chinese businessman who has invested in North Korean mines.

Dandong is home to many ethnic Korean Chinese traders who deal with both North and South Korean businessmen. It is also home to South Korean and western Christian missionaries trying to operate in North Korea.

U.S. President Barack Obama last week signed into law legislation broadening sanctions to punish North Korea for its nuclear programme, human rights record and cyber crimes. (Reporting by Ju-min Park and James Pearson in SEOUL and Clark Li in BEIJING; Editing by Tony Munroe and Michael Perry)