ALGIERS (AFP) - A senior Japanese official met Algeria's prime minister on Wednesday to press for an explanation of the gas plant siege, as Tokyo confirmed the deaths of two more nationals, taking its toll to nine.

Senior vice foreign minister Shunichi Suzuki arrived aboard a government jet that is to repatriate the bodies of those known to have been killed in the hostage crisis, along with the seven Japanese who survived.

Tokyo announced late on Wednesday that it knew for sure that nine Japanese were killed after Islamist gunmen overran the desert facility. One Japanese citizen remains unaccounted for.

"Unfortunately, we have been able to confirm two more deaths," said chief cabinet secretary Yoshihide Suga. "The Japanese government expresses sincere condolences to the families and people concerned."

"The use of violence cannot be tolerated for any reason. We firmly condemn acts of terror," he said adding the government would do its utmost to confirm the fate of the final missing person.

Seventeen Japanese were at the facility in In Amenas when jihadists struck last Wednesday at the start of a four-day siege that left dozens of foreigners dead. Seven of them made it to safety.

Mr Suzuki carried a letter to Algerian President Abdelaziz Bouteflika from Japan's Prime Minister Shinzo Abe, Mr Suga told reporters in Tokyo earlier.

As well as Prime Minister Abdelmalek Saleki, Mr Suzuki also met Foreign Minister Mourad Medelci, Japan's Kyodo News reported, citing Tokyo's foreign ministry.

Japan has asked Algeria to fully investigate events at the gas plant and exactly how individuals died, Suga said in Tokyo.

"Algeria has promised to cooperate as much as possible," he said.

Algeria has said 37 foreigners of eight different nationalities and an Algerian were killed in the siege, which ended on Saturday.

Several people are still missing and the bodies of others are so badly charred that they have not been identified.

Wednesday's visit came as it emerged that Britain, Japan, the United States and other countries whose nationals were caught up in the events at the In Amenas plant issued a joint demarche to Algeria last Friday.

A demarche is a formal diplomatic move in which a country's stance is conveyed in person - rather than by note - to another government.

In a conference telephone call, vice foreign minister Minoru Kiuchi told foreign minister Medelci that Tokyo wanted Algiers to do all it could to protect captives.

"Japan is strongly concerned about acts that put the lives of the hostages at risk, and it is regrettable that the Algerian government pressed military rescue operations," he said, according to the foreign ministry.

Japan was among the more forthright of nations as the hostage crisis unfolded, summoning Algiers' ambassador to demand answers and to push for military restraint as armed forces surrounded the plant.

The Japanese plane's arrival in Algiers came as Tokyo announced it was shutting its embassy in neighbouring Mali, evacuating staff and urging its nationals there to leave because of the deteriorating security situation.

The kidnappers claimed they launched their attack in protest at Algeria's complicity in a French military campaign against Islamists in Mali.

The Japanese death toll in Algeria - the highest in a terror attack since Al-Qaeda crashed airliners into New York's Twin Towers when 24 Japanese died - has shaken a country not accustomed to its citizens being made targets abroad.

There has been blanket media coverage of events half a world away and anguished demands for more to be done to protect Japanese working in trouble spots, including beefing up spy networks.

Kyodo on Wednesday said Mr Suga indicated Tokyo's willingness to consider increasing the number of defence attaches at Japanese embassies to strengthen the country's ability to gather information.

"I am aware of the need. We need to think about the most effective (crisis-response) measures," Mr Suga said.

Japanese media have given blanket coverage to the crisis and its aftermath as the country reels from its biggest death toll in an act of terror since the Sept 11 attacks of 2001.

On Wednesday, Kyodo published the first pictures to emerge from the incident, showing gun-toting kidnappers in camouflage, with their faces covered, guarding hostages at the desert site.