A global rights watchdog on Thursday called on Angola to halt mass deportations after more than 400 000 migrants mainly from the Democratic Republic of Congo fled or were expelled from Angola in just weeks.Human Rights Watch (HRW) says migrants have been targeted in a massive operation targeting diamond smuggling.Without producing evidence, the government of President Joao Lourenco has claimed that smuggling was organised and controlled by irregular migrants."Angola should stop forcing people to leave the country until it can provide individual assessment and due process guarantees to distinguish irregular migrants from refugees and registered migrant workers," said Dewa Mavhinga, the HRW southern Africa director in a statement.In a report, HRW said the government "should immediately suspend the deportation of refugees from the Democratic Republic of Congo, conduct a prompt and impartial investigation into alleged abuses by state security forces".The migrants have accused Angolan security forces of physical and sexual abuse that feed a climate of fear and intimidation.Angola is the world's fifth-largest diamond producing country.HRW pointed to UN reports that Angolan security forces and allied youth militias from the ethnic Tshokwe group, shot dead at least six Congolese last month during an operation in Lunda North province bordering DRC.The government has vehemently denied that its security forces committed abuses during "Operation Transparency". But the Angolan ambassador to the DRC, Jose Joao Manuel, has said his government was willing to investigate the allegations, according to HRW.The rights group also expressed fears that the sudden return of tens of thousands of refugees and migrants risked further destabilising southern Congo in the wake of national elections set to take place on December 23.DRC has an abundance of mineral wealth but is rocked by unrest unleashed by rebel groups and militias from within and neighbouring nations such as Uganda and Rwanda. Oil-rich Angola attracts hordes of Congolese as it is relatively stable and offers better employment prospects.Angola and DRC share a 2 500km land border, the longest in Africa.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.