UPDATE 1-Algeria sees no impact on investment after attack

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Jan 21 (Reuters) - An attack by Islamist fighters at Algeria's In Amenas gas complex will not prompt foreign energy firms to abandon investment in the country, Algerian Energy and Mines Minister Youcef Yousfi said on Monday.

"I don't think foreign workers are leaving Algeria definitively. They have left just to reassure their families," Yousfi told reporters in parliament.

"I don't think foreign companies will leave definitively."

He said the fighters had tried to blow up the gas plant.

"Sonatrach's executives halted production just after the start of the attack to avoid any impact of explosions. The terrorists tried to blow up the plant but in vain," he said.

He said a decision on the start-up date of the plant could be made on Tuesday.

(Reporting By Hamid Ould Ahmed; editing by Jane Baird; Editing by Anthony Barker)