Families of British embassy staff are being evacuated from Iran amid escalating clashes between security forces and demonstrators protesting over this month's disputed presidential election, it was announced today.

EMBASSY STAFF'S FAMILIES EVACUATED FROM IRAN

By Andrew Woodcock, Press Association Chief Political Correspondent

The Foreign Office has tightened its advice on travel to the country, warning British nationals against all but essential visits.

Riot police used tear gas and fired live bullets in the air to disperse a rally in central Tehran today, in an apparent sign that the regime of president Mahmoud Ahmadinejad is taking a tougher line with protests.

Near-daily rallies on the streets of the Iranian capital have drawn crowds numbering hundreds of thousands over the past week, but the elite Revolutionary Guard ordered demonstrators to end "sabotage and rioting activities" today and be prepared for a "revolutionary confrontation" with security forces if they continue their protests.

In a statement today, the Foreign Office said: "The ongoing violence has... had a significant impact on the families of our staff who have been unable to carry on their lives as normal. As a result, we are withdrawing dependants of embassy staff until the situation improves.

"We do not believe that it is necessary to reduce the number of staff at this time, however we are monitoring the situation with the utmost vigilance. The security of our staff is of paramount importance."

The statement said it was hoped that families could return "as soon as possible".

British citizens already in Iran have not been advised to leave the country, but are being warned to avoid demonstrations and large public gatherings.

The Foreign Office said diplomats were monitoring the situation with "the utmost vigilance".

Iran says at least 17 protesters have been killed in a week of unrest since the June 12 election, which has been denounced as a fraud by Mr Ahmadinejad's main challenger Mir Hossein Mousavi.

The country's highest electoral authority, the Guardian Council, acknowledged today that there were voting irregularities in 50 electoral districts, but insisted the problems do not affect the outcome of the vote.

The Foreign Office travel advice now reads: "Large-scale demonstrations following the Iranian presidential elections June 12 continue. There have been violent clashes at and after some demonstrations with some deaths. Further violence is possible.

"Some forms of international and internal communications have been disrupted, eg SMS, mobile telephone coverage and internet.

"You should avoid demonstrations and large public gatherings."