The European Union plans to impose more sanctions on the embattled government of Syrian President Bashar al-Assad over its crackdown on protesters.

The EU and the United States already have sanctions in place against Syria, and EU foreign ministers will vote Thursday to further restrict trade and economic dealings with Damascus.

The news of the sanctions came as tens of thousands of Syrians protested on Monday against unprecedented economic sanctions imposed by the Arab League on Sunday. Syrian state television showed rallies in the capital Damascus, as well as Aleppo and Hasake.

Syrian Foreign Minister Walid Muallem slammed the Arab League action in a televised news conference. He said the sanctions amount to “a declaration of economic war.” He also said the organization refuses to believe that there is a foreign conspiracy against Syria.

Arab officials proposed the sanctions after Syria refused to accept a Friday deadline they set to allow league observers into the country to monitor the government's response to the eight-month uprising.

Rights groups say Syrian forces killed at least 23 people across the country on Sunday.

The United Nations says more than 3,500 people have been killed since March in connection with the uprising.