Tanzania is seriously investigating allegations that it re-flagged Iranian oil tankers in defiance of sanctions.
A US congressman alleged last week that up to 10 Iranian oil tankers had been re-registered in Tanzania.
But the East African nation’s foreign minister said so far there was no evidence to suggest this was true and he appealed for help with the probe.
The US and the European Union have just tightened sanctions on Iran over concerns about its nuclear programme.