Students protesting Riyadh's military assault on Yemeni Shias in front of the Iranian Foreign Ministry have called for the expulsion of the Saudi ambassador.

According to IRIB World Service, the university students, who were demonstrating for the second consecutive day on Tuesday, made the demand in a letter addressed to President Mahmoud Ahmadinejad.

The letter referred to the anniversary of the 1987 killing of pilgrims.

The students who have gathered in Tehran from all over the country despite the cold weather in the capital plan to continue their sit-in until Wednesday.

One of the organizers of the event told IRNA that the students were there to show their anger at what they believed was a war planned by "Zionist" entities.

Student spokesman Esmail Tahmouresi said "The Zionists have instigated many wars in places like Afghanistan, Iraq and the Gaza Strip to cover their own losses," adding, "In the war against Shia Muslims in northern Yemen Saudi Arabia has become the perpetrator of the Zionist's colonialist plans."

The conflict in northern Yemen first began in 2004 between Sana'a and Houthi fighters, but relative peace had returned to region until August 11, when the Yemeni army began a major offensive, dubbed Operation Scorched Earth, against the province of Sa'adah.