Aljazeera aired a videotape on Monday from the "al-Taff Martyrs Brigades" which particularly threatened Kuwaitis in the southern Iraqi city.
The tape showed a group of masked men, some holding automatic rifles and one man reading a statement.
"All workers in foreign and Arab companies in Basra, especially Kuwaiti companies, are targets for killing and kidnapping," the man said. "We strongly warn them against going into the streets of Basra."
"These people are on par with American and British (occupation troops). They are all the same," he said as the other masked men cheered and chanted "Allah Akbar" (God is Greatest).
"All workers in foreign and Arab companies in Basra, especially Kuwaitis, are targets for killing and kidnapping"
Al-Taff Martyrs Brigades
Violence in Basra, which is near Iraq's southern border with Kuwait, has intensified in recent weeks after US-led forces cracked down on the militia of Shia cleric Muqtada al-Sadr.
Hundreds of Sadr's Mehdi Army fighters fought running battles with British troops in Basra on Saturday after suffering heavy losses in other Iraqi cities.
Oil exports from Basra's vital terminal were cut back by a sabotage attack on a pipeline on Saturday, two weeks after US-led forces foiled boat attacks on tankers at the terminal.
Dozens of foreigners have been seized in Iraq recently - some have been killed by their captors and others released.