Austrian Foreign Ministry spokesman Martin Weiss said the Friday afternoon attack occurred at the al-Ghani oil field, south of Sirte. Security teams retook the site, but nine foreign workers are unaccounted for, including one Austrian, one Czech and seven non-EU citizens.
No demands have been made by any group or individual for their return.
The Czech Foreign Ministry confirmed that a Czech national was missing after the attack. Ministry spokeswoman Michaela Lagronova said the ministry is contact with the family of the missing person and is co-operating with Austria.
The Czech Foreign Ministry said one of its officials would fly to the region as soon as possible, while Austrian officials said Foreign Minister Sebastian Kurz was conferring with high-ranking interior and defence ministry officials as well as the Austrian Embassy in Tunisa, which was overseeing Libyan affairs.
One of the officials said the attack had been on a site run by VAOS, an Austrian company that offers construction services to oil companies. Telephone calls to VAOS offices in Malta and in Libya weren't answered late Saturday.
Associated Press writers Frank Jordans in Berlin and Karel Janicek in Prague contributed to this report.