India said on Saturday it was in touch with Tehran to secure the release of 18 of its nationals serving on a British-flagged tanker seized by Iran in the Strait of Hormuz.

The Philippines also said it would ask Iran to free a Filipino crew member on the Swedish-owned Stena Impero which was seized on Friday, as tensions mount in a key waterway for the world's oil supplies.

Raveesh Kumar, spokesman for India's foreign ministry, told AFP that 18 of its nationals were on the ship and said New Delhi was “in touch with the government of Iran to secure (their) early release and repatriation”.

The tanker was impounded off Bandar Abbas port for breaking “international maritime rules” after colliding with a fishing boat, Iranian authorities said.

The Philippine foreign department said a Filipino, three Russians and a Latvian were also among the ship's crew.

“(Philippine) Ambassador to Iran Fred Santos is contacting Iranian authorities to seek assurance that the Filipino seafarer is safe and will be released soon,” it said, adding the unidentified crew member's family has been notified.

The recruitment agency that supplied the Filipino crew member told Manila there were no reported injuries as the vessel headed for the Iranian coast on Friday, the department added.

Iranian authorities said the tanker has anchored off Bandar Abbas with all its 23 crew aboard.