An Egyptian parliamentary committee has given initial approval to a proposal to amend the constitution in a way that would extend President Abdul Fattah al-Sisi's time in office, state media say.

Mr Sisi is due to stand down in 2022, when his second four-year term ends.

But a proposal from the majority bloc in parliament would lengthen future presidential terms to six years and let Mr Sisi stand for another two terms.

If approved by two-thirds of MPs, the changes would be put to a referendum.

In 2013, Mr Sisi led the military's overthrow of Egypt's first democratically elected president, Mohammed Morsi, following protests against his rule.

Since then, he has overseen what human rights groups say is an unprecedented crackdown on dissent that has led to the detention of tens of thousands of people.

Mr Sisi was re-elected last April after winning 97% of the vote. He faced no serious competition because several potential rivals dropped out or were arrested.

Article 140 of Egypt's constitution, which was approved in a referendum in 2014, currently states that the president serves four-year terms and may only be re-elected once.

As well as lengthening terms to six years, the amendment submitted on Sunday by the pro-government Support Egypt Coalition would allow Mr Sisi to serve an additional two terms after his current one ends, according to a copy posted on Facebook by one MP.

That would potentially allow the 64-year-old to stay in power until 2034.

Abdul Hadi al-Qudbi of the Support Egypt Coalition said it had acted "with a view of maintaining stability and continuing [Egypt's] developmental strategy".

On Tuesday, state-run Nile News TV quoted parliamentary Speaker Ali Abdul Aal as saying that the amendment had been approved by the General Committee after "fulfilling the required constitutional conditions".

The committee also approved other amendments that would create the post of vice-president, reintroduce a second chamber of parliament, and strengthen the representation of women, Coptic Christians and disabled people.

The 596-seat parliament is overwhelmingly supportive of Mr Sisi, but a small group of leftist MPs denounced the proposals, saying they would cancel out the principal gain of the 2011 popular uprising that ousted longtime President Hosni Mubarak.

"Project to amend #Egypt constitution unfolding & in full throttle," tweeted the Nobel Prize winner Mohamed ElBaradei on Monday. "Arab Spring in reverse!"