Several hundred Iranian students yesterday occupied the US embassy in central Tehran, taking up to 100 hostages, including US diplomatic staff, and Marine guards in an assault that appears to have left the Government nonplussed.

At a press conference late yesterday, spokesmen for the students who described themselves as Muslims without political party affiliations said that the staff would be held until the US Government agreed to return the deposed Shah to Iran to stand trial. If the request was not met, the students said they would act towards the hostages in accordance with the wishes of the people.

The attack came about midday after hundreds of thousands had marched through the centre of the capital in commemoration of students killed by the Shah’s troops at Tehran University last year. The occasion rapidly turned into demonstrations against the US Government for admitting the Shah in the US on medical grounds.

About 400 students were involved in forcing the gates of the embassy compound and scaling the walls. Iranian eyewitnesses said that a small group was heavily armed, but there appears to have been virtually no fighting as none of the students controlling the embassy last night carried weapons. A small group of Marine guards fired tear gas at the attackers but failed to check the students, who quickly took control of all embassy buildings.

Blindfolded hostages from the American embassy siege in Tehran, Iran, 1979. Photograph: Sipa Press/REX

Embassy staff who had locked themselves in a room on the upper floor of the main Chancery building surrendered. They were initially bound and blindfolded and led to another part of the embassy, but students said later that they had been untied, made comfortable, and supplied with food and drink.

The US chargé d’affaires, Mr Bruce Laingen, was not at the embassy at the time of the takeover. He has been in close contact throughout the day with the Foreign Minister, Mr Ibrahim Yazdi, who returned yesterday from Algiers. The Foreign Ministry is understood to have given assurances to the US Government that its nationals are safe and well, but there is no evidence of co-ordinated action by the Government and religious authorities to defuse the situation.

Students deny having had any contact with the government, although a foreign ministry spokesman said that an independent mediator has been sent to try to secure the release of the hostages.

There has been no formal government statement on the affair. But a foreign ministry comment described the student attack as “a national reaction to the US Government’s indifference to the hurt feelings of the Iranian people about the presence of the Shah in the US under the pretext of illness.”

The crisis ended on 20 January 1981 when 52 hostages were released. Three decades later, it was announced that financial compensation was to be awarded to those held in the embassy.