North Korea said on Sunday that the United States' push for sanctions following its fifth nuclear test was "laughable" and the country would continue to strengthen its nuclear power.

"The group of Obama's running around and talking about meaningless sanctions until today is highly laughable," state-run KCNA news agency cited a foreign ministry spokesman as saying in a statement.

The United States may launch unilateral sanctions against North Korea, a U.S. special envoy for the isolated state said earlier on Sunday, two days after it carried out its fifth and biggest nuclear test in defiance of U.N. sanctions.