By Kathryn Westcott BBC News Online

Ahmed Saadat, the 48-year-old secretary-general of the Popular Front for the Liberation of Palestine (PFLP), is the highest-ranking Palestinian political figure arrested by the Palestinian Authority.

He is a second-generation PFLP leader, belonging to what is known as the movement's 'insiders', those who stayed in the West Bank and Gaza rather than going into exile.

Mr Saadat served time in Israeli prisons

Mr Saadat, who trained as a maths teacher, is veteran of the first Palestinian intifada. He has spent some 10 years in Israeli jails, on eight separate occasions.

It is reported that it was his work with other detainees that led to his appointment to the PFLP's ruling body, its politburo.

"He has good contacts and is a man of the people. He is a charismatic figure," says Abdel Bari-Atwan, editor of pan-Arab newspaper al-Quds al Arabi.

Consolidation

His predecessor, Mustafa Abu Ali, was a member of the 'old guard' of exiled leaders based in the Syrian capital Damascus.

As a result, analysts say Mr Abu Ali was not as familiar with the situation on the ground in the Palestinian territories as his successor.

PFLP founder George Habash staunchly opposes the Oslo peace process

Mr Saadat took over as leader of the PFLP in October 2001, two months after Mr Abu Ali was assassinated in an Israeli attack on his office.

His election was widely seen as a move to consolidate the PFLP's presence in the West Bank and Gaza.

His predecessor is thought to have lacked the full backing of the PFLP membership.

Oslo

Mr Abu Ali move back to the Palestinian territories under Yasser Arafat's Palestinian Authority was seen as an indirect acceptance of the Oslo peace plan negotiated with Israel.

PFLP founder and former leader George Habash has maintained a staunch opposition to the peace process, which, among other things, has pitted the movement against Mr Arafat.

While Mr Abu Ali rejected the Oslo peace process, he did not do it strongly enough, said Mr Bari-Atwan. He also took a pragmatic approach and moved towards a reconciliation with Mr Arafat.

Mustafa Abu Ali "was not widely trusted as a leader"

Mr Saadat, however, is seen as a more radical leader and more loyal to the 'original' principles of Mr Habash. Both strongly support the aim of the destruction of Israel.

At the same time, he stated the goals of the Palestinian people at his inaugural press conference as "our right of return, and our independence, with Jerusalem as the capital.

When Mr Saadat took the up the reins of the PFLP, he vowed to avenge the assassination of Mr Abu Ali.

Raising the profile

Shortly afterwards, the group assassinated the right-wing Israeli tourist minister Rehavam Zeevi.

This, analysts say, was a popular move among militants and one that reinvigorated the organisation.

"Under Mustafa Abu Ali, the movement had become marginalised," Mr Bari-Atwan says.

"It had gone from being the second most important Palestinian group to forth or fifth. But the assassination was extremely important and raised the stakes among the PFLP's supporters and the Palestinians in general."

Other militant Palestinian groups have been quick to voice their opposition to Mr Saadat's arrest.

Recently, the factions had agreed to make national unity their main aim and the PFLP's leader's arrest appears to undermine this.

It is also significant because it appears to give a green light for the possible detention of leaders of other Palestinian militant groups.