British Prime Minister Tony Blair accused Iran today of seizing British naval personnel in Iraqi waters and said Tehran must understand its action was "unjustified and wrong".
"This is a very serious situation and there is no doubt at all that these people were taken from a boat in Iraqi waters," Mr Blair told a news conference after a European Union summit.
"I hope the Iranian government understands how fundamental an issue this is for us," he said.
"They should not be under any doubt at all about how seriously we regard this act, which was unjustified and wrong."
Iran detained 15 British Navy personnel at the mouth of the Shatt al-Arab waterway, which marks the southern stretch of Iraq's border with Iran, in the Gulf on Friday.
The seizure raised tensions that were already high with the West over Tehran's nuclear programme. The UN Security Council imposed new sanctions on Iran yesterday.
The Iranian government says the sailors strayed into its territory. But Mr Blair said: "It is simply not true that they went into Iranian territorial waters."
He said he hoped the issue could be resolved over the next few days, "but the quicker it is resolved, the easier it will be for all of us".
Britain's Ambassador Geoffrey Adams met Iranian Foreign Ministry official Ebrahim Rahimpour and requested access to the sailors, a British diplomat in Tehran said.
"We have repeated the line asking for their release. We asked for details of where they are and asked for consular access," the diplomat said.
"The (Iranian Foreign Ministry) promised to look into these requests and dialogue is continuing," the diplomat added.
Iranian television reported the meeting, without giving details. But it said the British envoy had been summoned. Iran's semi-official Fars news agency reported yesterday that the 15 sailors and marines had been transferred to Tehran. But this has not been independently confirmed.