Militants who seized an Algerian gas plant before they were killed in a bloodbath received logistical aid from Islamists in Libya, a well-informed source told AFP on Tuesday.
"Logistical support was provided from Libya," said the source close to hardline Islamist groups in Libya, which has seen a rise in extremism since the fall of Moamer Kadhafi.
The source did not specify the exact nature of such aid but acknowledged that Libyan Islamists were responsible for establishing contacts between the captors and the media.
International media groups, including AFP, were able to get from Islamist circles based in eastern Libya telephone numbers of the kidnappers as they last Wednesday overran the In Amenas gas plant in the deep Algerian desert.
Thirty-seven foreigners were killed in the four-day siege of the remote desert gas plant, some of them executed with a bullet to the head, Algerian premier Abdelmalek Sellal said on Monday.
He said that a total of 29 militants were also killed and three captured in the siege, which ended in a final showdown on Saturday when Algerian special forces stormed the sprawling gas complex.
Algeria has said its special forces managed to free 685 Algerian and 107 foreign hostages, most of them on Thursday, during their first rescue operation.
During the deadly standoff, several media outlets had talked of a "Libyan connection" to the siege.
Algerian website TSA cited a security source saying the kidnappers had entered Algeria from Libya in official Libyan vehicles, while other outlets argued that the weapons the kidnappers used came from Libya.
When questioned by AFP, Libyan officials simply reiterated the words of their prime minister, Ali Zeidan, who denied that the kidnappers entered Algeria from Libya, saying the Libyan territory was not being used for launching operations that threaten security of neighbouring countries.
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Algerian premier Sellal on Monday that the militants had crossed from northern Mali.
The Libyan source said that Libyan Islamists had no organisational link with the group, "Signatories in Blood" which led the four-day siege of the gas complex.
The group is led by one-eyed Mokhtar Belmokhtar, one of the founders of Al-Qaeda in the Islamic Maghreb (AQIM ). Belmokhtar left Al-Qaeda in October to create his own group.
Jaber al-Abidi, an analyst, has no doubt Libyans were involved.
"It is clear that there is a link between Libyan extremist groups and those who led the In Amenas operation," said Jaber al-Obeidi, an analyst and political activist.
"Libyan extremists are present in northern Mali and helped carry weapons from Libya after the fall of the regime" of Kadhafi, he added.
The "Signatories in Blood" group had said that its attack on the gas complex was in retaliation for French intervention in northern Mali.
Algeria's Sellal dismissed this, saying the assault had been planned for nearly two months, long before France intervened in northern Mali.
Since the fall of Kadhafi's regime in October 2011, Libyan Islamists have gained influence and inherited a large military arsenal from the conflict that ousted and killed him.
Their ability to strike was illustrated by the murderous assault launched September 11 on the US consulate in Libya's eastern city of Benghazi that killed the American ambassador Chris Stevens and three other Americans.
According to the Libyan source, the Islamists who attacked the gas facility entered Mali "transiting through Niger and Libya from the Salvador triangle," a barren stretch of desert that borders Libya, Algeria and Niger.
Libya has long struggled to monitor its 4,000-kilometre (2,500-mile) land border.