South Korea and Singapore have intercepted suspected nuclear and weapons materials bound for Iran that breach UN sanctions imposed on the Islamic republic, diplomats said on March17.

The two seizures, made in the past six months but only revealed now, add to a growing list of alleged Iranian attempts to breach an international arms embargo, which are bringing mounting pressure to tighten sanctions, they said.

"South Korea authorities found more than 400 suspicious tubes in a jet cargo at Seoul airport in December," one diplomat told AFP, giving details from a report to the UN Iran sanctions committee.

The tubes could be used for nuclear facilities, the diplomat said, speaking on condition of anonymity because the seizures have not been made public.

"In September, aluminium powder that can be used for rockets was found on a ship in Singapore harbor," the diplomat added.

In each case the product was destined for Iran.

The details were confirmed by a second envoy at the UN who said the sanctions committee would study them when it discusses the latest report from Iran experts monitoring the sanctions regime.

"This is going to add to calls for at least tighter implementation of the current sanctions," said the envoy, also speaking on condition of anonymity. "There are still too many countries not applying the measures."

The United Nations has passed four rounds of sanctions against Iran for its refusal to halt uranium enrichment, including a global arms embargo.