By Lamine Chikhi

ALGIERS (Reuters) - Many people were killed when Algerian forces opened fire on a vehicle at a remote gas plant where gunmen were holding dozens of Western hostages, a resident of the locality and Arab news reports said on Thursday.

The resident, who asked not to be identified, said there were many bodies at the scene. He did not give firm numbers of the dead or say whether they were kidnappers, hostages or both.

Mauritania's ANI news agency, which has been in constant contact with the kidnappers, reported that 34 of the captives and 15 of the captors had been killed when government forces fired from helicopters while the kidnappers were trying to move some of their prisoners.

Qatar-based Al Jazeera television carried a similar report. Those details could not be immediately confirmed.

ANI quoted a spokesman for the kidnappers as saying they would kill the rest of their captives if the army approached.

Governments around the world were holding emergency meetings to respond to one of the biggest international hostage crises in decades, which sharply raised the stakes in a week-old French campaign against al Qaeda-linked rebels in the Sahara.

An Algerian security source earlier said 25 foreign hostages had escaped the besieged compound, including two Japanese.

The source told Reuters the captors had demanded safe passage out with their prisoners. Algeria has refused to negotiate with what it says is a band of about 20 fighters.

A group calling itself the "Battalion of Blood" says it seized 41 foreigners, including Americans, Japanese and Europeans, after storming the gas pumping station and its employee barracks before dawn on Wednesday.

The attackers have demanded an end to the French military campaign in Mali, where hundreds of French paratroopers and marines are launching a ground offensive against rebels a week after Paris began firing on militants from the air.

(Reporting by Lamine Chikhi; Writing by Peter Graff; Editing by Giles Elgood)