By Ercan Gurses

ANKARA, May 18 (Reuters) - The United States and United Nations expressed deep concern on Monday about the death sentences handed down in Egypt for President Mohamed Mursi and other Islamists, while Turkey warned of Middle East turmoil if they are carried out.

U.N. Secretary-General Ban Ki-moon said he will closely monitor the appeals process for the death sentences and urged actions that would promote the rule of law.

The U.S. State Department said Egypt's practice of mass trials and sentences was unjust and often used against members of the opposition or non-violent activists.

"We are deeply concerned by yet another mass death sentence handed down by an Egyptian court to more than 100 defendants, including former President Mursi," State Department spokesman Jeff Rathke told reporters in Washington.

An Egyptian court on Sunday sought the death penalty for Mursi and 106 supporters of his Muslim Brotherhood, in connection with a mass jail-break in 2011. A final ruling is expected on June 2.

In Ankara, Turkey's presidential spokesman warned the Middle East would be thrown into turmoil if Egypt carried out its death sentences.

Ibrahim Kalin said the sentences were a "breach of justice" and called on the international community to speak out more strongly against them.

"The subject demands universal attention. The execution orders and carrying them out will push the Middle East into turmoil," he told reporters.

Turkey would work with the U.N. Human Rights Commission after the sentences, and take "all necessary steps," he added.

Turkish President Tayyip Erdogan is a supporter of Mursi, Egypt's first democratically elected president, and relations with Egypt have soured since the army forced Mursi from power in 2013.

Diplomatic ties between the former regional allies were broken off after Erdogan repeatedly accused the new Egyptian government of carrying out a coup.

Speaking to Egypt's state news agency, an unidentified Egyptian official said Cairo was not surprised by Turkey's comments.

"The current regime in Turkey is a reflection of the ideas of the terrorist Muslim Brotherhood," the official added.

The Turkish government's backing for the Muslim Brotherhood and Islamist groups across the Middle East has harmed Ankara's relations with other regional partners, including Saudi Arabia and Libya, since the Arab Spring erupted four years ago. (Reporting by Ercan Gurses and Tuvan Gumrukcu inAnkara, Shadi Bushra in Cairo and Doina Chiacu in Washington; editing by Andrew Roche and David Gregorio)