British officials in Iran have denied claims of UK involvement in two bomb attacks which killed at least four people on Saturday evening.
The two bombs left at least four people dead and scores injured
The British embassy in Tehran condemned the attacks in Ahwaz, in the province of Khuzestan near the border with Iraq.
It said Britain rejected allegations made in the past about links between the British government and what it described as terrorist outrages.
Britain believes Iranian weapons have been used to target UK forces in Iraq.
Iranian media quoted various military and political officials as saying the attacks were the work of the British.
The statement from the British embassy on Sunday said: "There has been speculation in the past about alleged British involvement in Khuzestan.
"We reject these allegations. Any linkage between the British government and these terrorist outrages is certainly without foundation."
Iran's foreign ministry spokesman said the bombings were being investigated.
"Unlike the British we are not going to express our views without the necessary investigations," spokesman Hamid Reza Asefi said.
"We don't talk without proof and documentation," he said, in reference to Tehran's complaints that the UK has not provided evidence to support its accusations about Iran's alleged involvement in Iraq.
Student news agency ISNA reported Alaeddin Borujerdi, head of Iranian parliament's foreign policy commission, as saying: "Since there are British troops present alongside our border, there is a concern over their involvement in the explosions in Ahwaz."
Deputy Interior Minister Mohammad Hossein Mousapour told the Mehr news agency that "most probably those involved in the explosion were British agents who were involved in the previous incidents in Ahwaz and Khuzestan," the AFP news agency reported.
Six bombs exploded in June in Ahwaz, killing at least 10 people, days before Iran's presidential election.
A senior official said Americans were behind those attacks and also suggested that Britain might be involved - but he gave no evidence to support his claims.
Meanwhile, Foreign Secretary Jack Straw has repeated the prime minister's accusation that Iranian weapons have been used to target British forces in Iraq recently.
Although Tony Blair originally said that he "couldn't be sure" of this, Mr Straw told a press conference on Sunday that explosives which killed at least eight British soldiers did originate from either Hezbollah or Iran.
He brushed aside Iranian comments that the explosives might have been left behind in Iraq as a result of the eight-year war between Iran and Iraq.
Violence has erupted in Khuzestan earlier this year
"There were improvised explosive devices used against a number of British convoys which killed, probably at least eight British soldiers and soldiers from other parts of the coalition.
"The forensic examination of those devices linked their design to Hezbollah and to Iran. That's the evidence we've put to the Iranians."
The BBC's Frances Harrison in Tehran said no one had claimed responsibility for the Iranian bombs, which were homemade devices.
Ahwaz is the capital of the oil-rich province of Khuzestan, dominated by ethnic Arabs.