Lebanon believes Saad al-Hariri, who resigned as prime minister on Saturday while in Saudi Arabia, is being held by Riyadh, and Beirut plans to work with foreign states to secure his return, a top Lebanese government official said yesterday.

A second source, a senior politician close to Saudi-allied Hariri, said Saudi Arabia had ordered him to resign and put him under house arrest. A third source familiar with the situation said Saudi Arabia was controlling and limiting his movement.

Hariri's shock resignation, read out on television from Saudi Arabia, pitched Lebanon into a deep political crisis and pushed the country back to the forefront of a regional struggle between Saudi Arabia and Iran.

It has fueled speculation in Lebanon that the Sunni Muslim politician, long an ally of Riyadh, was coerced into stepping down by the Saudis.

Saudi Arabia and members of Hariri's Future Movement have denied reports that he is under house arrest. But he has put out no statements himself denying his movements are being restricted. He made a one-day flying visit to the United Arab Emirates earlier this week before returning to Saudi Arabia.

Hariri's office said in statement he had received the French ambassador to Saudi Arabia yesterday. He had also met the head of the EU mission to Saudi Arabia on Wednesday, and on Tuesday the British ambassador and the US charge d'affaires.

Saudi Arabia says Hezbollah, which was included in Hariri's coalition government, had “hijacked” Lebanon's political system.