Video footage appeared to show a crowd of pro-Assad demonstrators in Latakia surrounding and climbing onto the white vehicles used by monitors.
More than 160 monitors from the regional body have been deployed in Syria since President Bashar al Assad agreed a deal to end a crackdown on anti-regime protests by the security forces.
The attack came just hours after Mr Assad gave a two-hour speech on state TV, in which he vowed to use an “iron fist” to defeat what he claimed were “terrorists” trying to destabilise the country as part of an international “conspiracy”.
Mr Assad also claimed he still had the support of the Syrian people and refused to step down.
“I will only leave this position when all of the people want me to,” he said in the speech at Damascus University.
He told the invited audience that there had been many deaths in Syria over the past 10 months and that he had been “hurt” by this. But he once again blamed the violence on foreign-backed terrorists.
“They have started killing innocents. They are killing the Syrian people,” he said.
Contradicting the testimony of numerous army defectors, he denied government troops had been authorised to use lethal force against protesters.
The speech was his fourth since the uprising began in March and the first since the Arab League monitors arrived.
Mr Assad lashed out at the regional body which he said had a long history of failing to protect Arab and Syrian interests.
“When have the Arabs ever stood with Syria?” he asked.
But Assad insisted that the Arab League had more to lose by kicking out Syria than the Syrian people who he said were “the heart of the Arab World”.
He said his government had two main policies: carrying out reforms and fighting terrorism. He said the terrorists had no interest in reform.
The 46-year-old, who is facing the biggest challenge of his 11 years in office, is trying to quell dissent by promising a new multi-party system, a new constitution and parliamentary elections.
He said a referendum on the constitution should be held in March, and elections two to three months later.
The president dismissed calls for a Government of National Unity, saying that such things were only needed in countries which were deeply divided or in a state of civil war.
He said he was ready to talk to the opposition but claimed some parts of the opposition were not interested in talks.
The opposition Syrian National Council (SNC) branded Mr Assad’s speech an “incitement to violence”.
“Our concern today is that such a speech is quite indicative of the total dismissal by the regime of the international community,” Basma Qadmani, a member the largest opposition umbrella group, said at a press conference in Istanbul.
The UN’s human rights chief has accused the regime of committing “crimes against humanity” with a systematic campaign of killing, incarceration and torture.
The UN is expected to discuss the situation in the country later.