PARIS - President Abdel Fattah al-Sisi has overseen a crackdown on dissent that is unprecedented in Egypt, and an election next week looks set to return him to power for the long term, a Human Rights Watch official said on Wednesday.

Sisi is expected to the March 26-28 ballot by a huge margin given all opposition candidates bar one have dropped out, and the sole remaining challenger has said he supports the president.

"The government arrested the key challengers or intimidated them out of the election race," Amr Magdi, Egypt researcher for the rights group, told Reuters in Paris.

"The way things are going tells us that (Sisi)... will be keen on staying in power. You may see the government producing amendments to reduce term limits and introduce more repressive tools."

His supporters say Sisi has improved security since 2013, when as army chief he overthrew Islamist President Mohamed Mursi, though the army Egypt has failed to end an Islamic State insurgency in the North Sinai region.

Critics say Sisi's popularity has been damaged by austerity reforms and a crackdown on political opponents, activists and independent media.

Magdi said the repression was worse than under autocratic former President Hosni Mubarak, who was toppled in an uprising seven years ago. "It is an unprecedented human rights and political crisis in the country," he said.

According to HRW, at least 60,000 people are being held on political grounds with some 15,000 civilians subject to military trials since October 2014.

Magdi said there had been a spike in death penalty sentences since 2015 as cases stemming from the end of the Mursi period were now being closed. Since December, 28 people had been executed.

"It's easy to marginalise and isolate violent people, but peaceful activism is the government's main concern," Magdi said.

(Reporting by John Irish; editing by John Stonestreet) ((john.irish@thomsonreuters.com; 0033-1 49 49 53 42;))