Iranian director Asghar Farhadi has won the best foreign language Oscar in Los Angeles, for a second time, for domestic drama The Salesman. Farhadi, 44, did not attend the ceremony because he said that the conditions that would be attached to a potential entry visa were unacceptable.

The director had originally planned to travel to Hollywood for the prize-giving to highlight “the unjust circumstances that have arisen for the immigrants and travellers of several countries to the United States”.

The surge in votes for his film was thought by some to be a registration by Oscar voters of a protest against Donald Trump’s travel ban, which aimed to prevent people coming to the US from seven Muslim-majority countries. On Sunday evening in London, a free screening of The Salesman was introduced by London mayor Sadiq Khan.

Until the ramifications of the ban for film-makers such as Farhadi became clear, Germany’s Toni Erdmann had been the strong favourite to take the prize. The other nominees were Land of Mine (Denmark), Tanna (Australia) and A Man Called Ove (Sweden).

The Salesman premiered at Cannes last May, where it won best actor for Shahab Hosseini and best screenplay for Farhadi – despite moderate notices from critics. The film follows a couple in Tehran involved in an amateur dramatic production of Arthur Miller’s The Salesman, who are forced to move apartments following an earthquake. But the flat into which they move has an unhappy history, compounded by an unwelcome intruder.

Farhadi won Iran’s first Oscar for his film A Separation in 2012. This second award puts him in an elite category of double-winners in the category, including Federico Fellini and Ingmar Bergman.

Iran’s first person in space, Anousheh Ansari, read out a statement from Farhadi at the podium: “ My absence is out of respect for the people of my country, and those of the other six nations who have been disrespected by the inhumane law that bans entry of immigrants to the US.”