Thousands of African migrants are protesting Israel's plan to deport them to an unnamed African destination.

Thousands of African asylum seekers and their local supporters are protesting against an Israeli plan to deport them.

The Israeli government has given the migrants until April 1 to leave the country for an unnamed African destination in exchange for $3,500 and a plane ticket, or they will be incarcerated indefinitely.

The Africans, nearly all from dictatorial Eritrea and war-torn Sudan dread over the looming expulsions after being institutionally mistreated inside Israel.

Israel considers the vast majority of the nearly 40,000 migrants to be job seekers and says it has no legal obligation to keep them. Critics have called the government plan unethical and a stain on Israel's image as a refuge for Jewish migrants.

Organisers say some 15,000 gathered in south Tel Aviv Saturday.

Israeli police arrested two suspects, one armed, on Saturday following racist threats to disrupt a migrant march that went ahead this weekend in Tel Aviv.

The threats were made online to target protesters at a demonstration against controversial plans to deport African migrants from Israel.

The men were "detained for questioning", police said in a statement.

"Friends it's happening... the battle to throw out the infiltrators... It's time to riot and defend our home," the post read.

One of the comments in response to the post read: "I am armed."

Israeli police swooped on the suspects before the migrant rights' rally was held.