Yemen has begun the trial in absentia of the brother of a leader of an armed group embroiled in a battle for autonomy in the country's north.

Yahya al-Houthi, who's brother Abdul-Malik al-Houthi leads the fighters, who are from the Shia Zaidi sect of Islam, went on trial on Monday on charges of spying for a foreign nation.

The court in Sana'a, Yemen's capital, alleged that al-Houthi was part of an "armed gang that ... carries out killings, explosions, destruction, looting and espionage in favour of a foreign country".

It was not stated which nation al-Houthi was accused of working for, but the government has accused Iran of supporting the Houthi fighters in the past.

The court also accused al-Houthi of "planning to assassinate a number of figures including the American ambassador in Sana'a".

The prosecutor's representative called for the maximum sentence against al-Houthi - the death sentence.

Yahya al-Houthi, a former parliamentarian who left Yemen to live in Germany three years ago, was stripped of his parliamentary immunity from prosecution two weeks ago in order for the trial to go ahead.

Charges denied

He has denied all of the charges against him.

"The accusations against me are nothing but lies," he said on the on a fighter's website.

The court is to appoint a lawyer for al-Houthi, and the trial will restart on November 2, after the defence has had time to research the case and form a team.

Al-Houthi rebels initially began fighting for a return to autonomous rule in the north in 2004, but the conflict intensified last August when the rebels stepped up the pressure on government forces.

The military responded with Operation Scorched Earth and Sana'a has vowed to crush the Houthis.

The rebels have said that they have been politically, economically and religiously marginalised by the government, who they have said is corrupt.

Thousands of people have died and at least tens of thousands have been displaced due to the conflict, according to the Red Cross and UN.