The first signs of a power struggle in Syria emerged yesterday when the late president's disgraced brother challenged the succession to power of his 34-year-old nephew, Bashar al-Assad.

Rifaat al-Assad, who in 1983 attempted a coup d'etat , threatened to return from exile in France to Damascus "at the appropriate time". He claims that his dismissal as vice-president in 1998 was "an illegal act" and that he - rather than Bashar - should have succeeded to power.

"What is happening in Syria is a real farce and an unconstitutional piece of theatre which is a real violation of the law and the constitution," Rifaat said through his spokesman in Marbella, Spain.

The spokesman, al-Hareth al-Khair, added: "Rifaat Assad is a leader of the Syrian people, [he] loves his people as his people love him. He will go to his people and take up his responsibilities to fulfil the will of the people.

"He represents legitimacy in Syria," Mr Khair said, adding that Rifaat is therefore capable of removing the restrictions against him "through the force of legitimacy, the people and the army who are with him".

He added: "Dr Rifaat stresses peaceful action and refraining from spilling blood and does not want Syria to drown in blood. But he believes that legitimacy will prevail in a rightful way."

The Syrian military, however, appears to have rallied around Bashar.

The pan-Arab newspaper, al-Hayat, yesterday quoted a senior official as saying orders had been issued to arrest Rifaat if he tried to attend his brother's funeral. The army and the security services were granted "full powers to carry out anything to stop him from entering the country", the official said.

Security has been stepped up at Beirut airport and at Lebanese seaports; security officials there said Syrian agents were on the lookout for Rifaat in case he tried to sneak home through the porous Lebanese border.

Commenting on the threat of arrest, Rifaat's spokesman said: "This is natural to come from a leadership that has no confidence in itself. We expect more."

After his sacking as vice-president, Rifaat, 63, took refuge in France, where surveillance has been sharply stepped up, according to French secret service sources.

Rifaat has been told formally that he will be expelled from the country if he starts moves to return to Damascus and challenge Bashar. "If he is told to leave the country, he will probably seek refuge in London where his son, Soumar, runs the television station, ANN, which is linked with studios in Paris," an agent in the surveillance team said.

The decision by the French president, Jacques Chirac, to attend Hafez's funeral as the only western head of state was seen by diplomats here as proof that France was committed to Bashar's succession as part of a long-running attempt to re-establish French influence in the Middle East.