CAIRO, Sept 11 (Reuters) - The sons of former Egyptian president Hosni Mubarak, Alaa and Gamal, and his last prime minister, Ahmed Shafik, have had charges they were involved in illegal land purchases referred to a criminal court, judicial sources said on Tuesday.

Shafik, who stood against Muhamed Mursi this year for the presidency, was put on a "watch list" last month by a judge who also said Shafik would be detained at the border on his return for allegedly allocating 40,000 square metres of land to Alaa and Gamal Mubarak.

Mubarak's sons are in prison awaiting trial on other corruption charges.

In May, Egyptian authorities announced the two would face charges along with seven other men of violating stock market and central bank rules to make unlawful profits through the dealing in shares of Al Watany Bank of Egypt.

Dozens of legal cases have been filed against Mubarak associates since he stood down on Feb. 11, 2011, after days of mass protests.

The one against Shafik was lodged in May by Essam Sultan, a leader of the Islamist Wasat Party, who accused the ex-airforce chief of exploiting his former position as head of the Young Air Force Officers Association to sell land owned by the association to Mubarak's sons at reduced prices.

Shafik denied the charge and said the decision to place him on a watch list was political. (Reporting by Shaimaa Fayed; Editing by Alison Williams)