British Foreign Secretary Philip Hammond has reopened the UK embassy in Tehran in a symbolic ceremony marking improvement of mutual ties between the two countries.

The British foreign secretary arrived in the Iranian capital, Tehran, on Sunday and entered the embassy building immediately after his arrival.

Hammond attended the reopening ceremony shortly afterwards at the embassy’s garden with Ajay Sharma, the new chargé d'affaires who will be Britain's top diplomat in Tehran.

Hammond also raised the UK flag at the garden of the diplomatic residence following four years of severed diplomatic relations.

Hammond's trip is the first visit to Iran by a British foreign secretary since 2003.

British Foreign Secretary Philip Hammond (C) arrives in Tehran, Iran, on August 23, 2015. © Mehr News Agency

The Iranian embassy in London will be also reopened on Sunday in the presence of Iran's Deputy Foreign Minister Mehdi Danesh-Yazdi.

Iran and Britain are expected to appoint ambassadors in the coming months.

During his two-day stay in Tehran, the British foreign secretary will hold talks with Iranian President Hassan Rouhani, Foreign Minister Mohammad Javad Zarif, Minister of Petroleum Bijan Zanganeh, Parliament (Majlis) Speaker Ali Larijani and Governor of the Central Bank of Iran Valiollah Seif.

Hammond and Zarif will take part in a joint press conference later on Sunday.

Britain shut down its embassy in Tehran in November 2011 and withdrew its diplomatic staff after hundreds of Iranian students staged a protest outside the British embassy in Tehran against the expansion of UK sanctions on Iran, pulling down the UK flag and demanding the expulsion of the British ambassador.

In late November 2011, Iran’s parliament (Majlis) approved a bill to downgrade the diplomatic ties between Tehran and London to the level of chargé d'affaires, and limit all economic and cultural collaborations to the minimum level.

Nearly two years after their diplomatic ties were severed, Iran and Britain agreed in October 2013 to appoint non-resident chargés d’affaires as a first step toward reestablishment of their ties.