Iranian authorities have stepped up security at the British, Turkish and Swiss embassies in Tehran after receiving warnings of possible terrorist attacks.

Iranian newspapers reported last week that the al-Qaida terrorist network has threatened to attack some western embassies in the capital.

Tehran's top security official, Ali Tala, said increased security arrangements were put in place around the three embassies. Police patrolled outside the buildings and barricades were placed on nearby streets.

A spokesperson for the Swiss embassy confirmed the additional security measures. The Swiss mission represents U.S. interests in Iran because Washington and Tehran severed diplomatic relations, after hard-line Iranians seized the U.S. embassy following the 1979 Islamic revolution.

Turkey requested extra security after last month's suicide bombings of British and Jewish targets in Istanbul.

The British embassy in Tehran was also targeted for shooting attacks in August and September.

Some information for this report provided by AFP and Reuters.