KABUL: Relations between Afghanistan and Iran have been strained by Kabul's strategic pact with the United States, officials said Tuesday, charging that Tehran has stressed Afghan diplomats in recent weeks.

And in parliament, lawmakers warned Iran to end its “interference” in Afghanistan's internal affairs over the Strategic Partnership Agreement signed last week by President Hamid Karzai and US President Barack Obama.

Tehran’s ambassador had urged some members of parliament not to vote for the deal, said Abdul Rahoof Ibrahimi, the speaker of the lower house, or Wolosi Jirga.

Afghan diplomats in the Iranian capital Tehran have been “constantly intimidated” since the deal with the United States was signed, a senior government official told AFP.

“They are being chased by Iranian security forces all over the place. Their movements have been restricted,” the official said, requesting anonymity because of the sensitivity of the issue.

“This is all to do with the (US-Afghan) strategic pact. They are unhappy,”the official said.

Foreign ministry spokesman Janan Mosazai acknowledged “problems” faced by Afghan embassy staff in Tehran, saying his ministry was investigating the situation.

“The problem is not posing any danger to our (embassy) staff there,” Mosazai told AFP, but refused to provide further details. He said his ministry was in talks with Tehran to solve the problem.

Iranian foreign ministry spokesman Ramin Mehmanparast publicly denounced the Afghan-US agreement at the weekend.

“Not only will the strategic pact not resolve Afghanistan's security problems, but it will intensify insecurity and instability in Afghanistan,” he said in a statement.

He described the pact as a source of “concern” for Iran as “the status of US military bases in Afghanistan is unclear and the security duties of US forces lack transparency”.

The strategic partnership agreement covers relations between Washington and Kabul for 10 years after most US troops pull out of the country in 2014, leaving the fight against Taliban Islamists to Afghan security forces.

It states that the United States will not use its presence in Afghanistan to launch offensive actions against neighbouring states, but leaves open the option of retaliation in the event of threats to Afghanistan.

Details of the number of US troops who may remain in the country after 2014, and their status, are yet to be worked out in a separate security pact.

Trust between the two neighbours has reached its lowest level since the 2001 US-led invasion that toppled the Taliban regime, the Afghan official said.

Tehran’s new envoy, Abolfazl Zohrehvand, who submitted his credentials to Karzai late last month, “is very arrogant, he behaved very undiplomatically,” the official said.

In another indication that ties are souring between the two countries, an Afghan security official told AFP that an Afghan journalist working for an Iranian news agency had been arrested as an alleged spy.

The National Directorate of Security, Afghanistan’s main intelligence agency accuses the Afghan reporter of spying for Iran, the official told AFP.

“We have hard evidence that he was passing on classified government documents to the Iranian embassy,” the official said. Karzai last week urged Iran to respect his country's partnership with the United States, saying “Afghanistan has paid a price” to maintain ties with its neighbours.

“We hope our neighbors understand this,” he said.