Thousands of Lebonese troops and police mobilized Thursday to block an unauthorized demonstration outside the US Embassy aimed at protesting "American-British collusion" with Israel in a dramatic prison raid in Jericho earlier this week. Several thousand troops in armored vehicles and police in trucks deployed to major roads north and south of Beirut, setting up checkpoints to search cars for weapons and check identification of passengers, security officials said. Traffic began to back up for miles on the coastal highway, according to witnesses. Similar measures were taken in southern Lebanon, with witnesses reporting troops blocking roads leading out of Palestinian refugee camps in the port city of Sidon to prevent protesters from heading to Beirut. Authorities appeared to be preventing the demonstrators from reaching the embassy, which is located in the hilly suburb of Aukar north of the city. Only a few protesters managed to get to the coastal road, down the hill from the compound. Two of the organizers, Mohammed Safa and Bassam Kintar, were detained by police, the two said by cellular phone to the al-Manar TV station. The security measures signified a new and tougher stance by authorities against protests by groups not allied with the government. Acting Interior Minister Ahmed Fatfat said organizers did not seek required permission. "They are not allowed to normally demonstrate," he said. "But at the same time we do not seek to ban legal protests." Fatfat warned that security forces would take action if protesters resort to violence. "The security forces, with the help of the army, will provide security for the people if the law is broken," he said on LBC television. The demonstration was called by the Arab Organization for Defending Detainees and other groups to protest the raid in the West Bank town of Jericho in which Israel spirited away six terrorists, including Ahmed Saadat, the alleged mastermind of the 2001 assassination of an Israeli Cabinet minister. The protest was "in solidarity with the struggler Ahmed Saadat and his comrades," the Arab Organization for Defending Detainees said in a statement. The US Embassy has been a frequent target of protests by anti-American Muslim Lebanese and Palestinian groups. Most of the demonstrations are peaceful, but a February 5 protest in Beirut by Islamic groups outside the Danish mission turned into a riot in the city's Christian sector, heightening sectarian tensions. That demonstration was against caricatures of the Prophet Muhammad published in Danish newspapers that sparked protests across much of the Muslim world.