Turkey has urged Iran and Azerbaijan to calm a row over a disputed territory in the oil-rich Caspian Sea, the Turkish Foreign Ministry said yesterday.

An Iranian gunship and a military aircraft last month ordered two Azeri research vessels hired by British oil company BP to retreat from an oil field claimed by both Iran and Azerbaijan as their own.

Turkey's Foreign Ministry said it had sent a message to the Iranian ambassador in Ankara urging Iran to abide by UN principles, abstain from the threat of force and settle the dispute through dialogue.

"We are carefully and closely watching the latest tension between our two neighbours Iran and Azerbaijan (that arose) because the legal status in the Caspian Sea is not yet clear," the ministry said in a statement.

A 1,700 kilometres oil pipeline from Azerbaijan capital Baku to the Turkish Mediterranean port of Ceyhan has received backing from the United States, which wants a Caspian oil export route to bypass Iran.

BP, which is developing the Azeri fields, supports the Baku-Ceyhan pipeline. The five states with Caspian coastline are at loggerheads on how to divide up the sea's oil-rich territory. But the disputes have not deterred Western oil companies keen to develop the Caspian's vast energy resources.