More than 3,900 people - including 1,650 migrants - have been arrested in South Africa during a police crackdown following April's deadly xenophobic violence, authorities have said.

"We are satisfied that we have stabilised the situation and further loss of life has been prevented," the government said in a statement released on Sunday.

"Security agencies continue to work around the clock to protect both foreign nationals and South African citizens against any attacks."

Some 2,260 South Africans have also been arrested on a variety of charges since the operation began.

"We will, in the next weeks and months, accelerate our efforts to take back public buildings that have been hijacked, either by foreign nationals or by South Africans; rid our townships and villages of drugs... that are destroying the lives of many young people," the government statement said.

The crackdown came after at least seven people were killed as mobs hunted down migrant workers from Zimbabwe, Mozambique and other African countries, forcing hundreds of terrified families to abandon their homes.

The arrests of the so-called "illegal" migrants have prompted concerns that the government is fanning xenophobic sentiment, though authorities have denied that the operation targeted foreigners.

In April, authorities launched a joint operation between the police, Ministry of Home Affairs and the army, targeting undocumented foreign nationals across the country. Human Rights groups and activists have described Operation Myala, that has resulted in at least 750 arrests so far, as "state xenophobia".

The police operation was strongly criticised during a rally on Saturday in a migrant neighbourhood in Johannesburg.

"Its timing, coming in the wake of the violent attacks targeting in particular people of African origin, feeds into the misconceptions that migrants are to blame for all our social and economic ills," said Zwelinzima Vavi, ex-secretary general of the Congress of South African Trade Unions.

Zimbabwean activist Elinor Sisulu also described the operation as a kind of "ethnic cleansing".

"Any state operation which was the image of cleaning or cleansing I find very disturbing, and I think the timing of it is absolutely unfortunate. Even if there was any merit in the operation, the timing [of Operation Fiela] is completely wrong," Sisulu told IOL media.

"There's been ethnic cleansing. In Rwanda, there was talk of cleaning out 'cockroaches' and I've actually heard people talking about cleaning out [here]."

Rampant unemployment and poverty are seen as an underlying cause of the violence by South Africans who have accused migrants of stealing their jobs.

More than 400 Mozambicans were expelled on Friday and 427 others in South Africa illegally are expected to be deported in coming days.

While Jacob Zuma, the South African president, has denounced the anti-immigrant violence, he also promised to step up a crackdown on illegal immigration.

Since the end of apartheid, South Africa has attracted millions of migrants fleeing political and economic turmoil in their own countries.

Source: Agencies