Saudi Arabia has been accused of declaring war on Lebanon by the leader of Hezbollah, according to Israeli newspaper Haaretz.
Hezbollah leader Hassan Nasrallah said the Lebanese Prime Minister Saad Hariri was being detained in Riyadh.
The UK Foreign Office website currently advises that the security situation in Lebanon "can deteriorate quickly".
The FCO advises travellers: "Demonstrations and other forms of civil unrest can occur at short notice and often turn violent. Lebanese issues or regional and international developments can have an impact on the local security situation. Monitor local media and avoid all protests."