The United Nations human rights office has expressed "deep shock" and concern over the reported executions of 20 people in Egypt over the past two weeks.

Due process and fair trial guarantees appear to have been disregarded, the UN High Commissioner for Human Rights (OHCHR) noted in a statement issued on Friday.

On January 2, five men were reportedly hanged in Alexandria after being sentenced to death by an Egyptian military court; four had been convicted over a 2015 blast in Kafr al-Sheikh that killed three military recruits and injured two others.

"We understand the defendants were tried by military judges on the basis of legislation that refers cases of destruction of public property to military courts and in view of the victims being from the Egyptian Military Academy," OHCHR spokesperson Liz Throssell told reporters in Geneva. "Civilians should only be tried in military or special courts in exceptional cases."

Previously, on December 26, a group of 15 men convicted on "terrorism" charges over the 2013 deaths of soldiers in the Sinai Peninsula were executed.

Military courts typically deny defendants the rights afforded by civilian courts, Throssell said, citing reports "that the prisoners who were executed may have been subjected to initial enforced disappearance and torture before being tried".

The UN human rights office has urged Egyptian authorities to "reconsider" the use of the death penalty, noting that executions "should not be used as a means to combat terrorism".

Increase in executions

According to figures from Cornell University's Death Penalty Worldwide, there has been a sharp increase in executions in the years since Egyptian President Abdel Fattah el-Sisi took power.

From 2011, the year that former President Hosni Mubarak was deposed, to 2013, Egypt executed one person.

In 2014, Egypt executed 14 people. The following year, 22 more people were executed, and at least 44 people were executed in 2016.

Sisi's government has also overseen an increasing crackdown on journalists in Egypt. Reporters Without Borders placed the country at 161 out of 180 countries in terms of press freedom.