KENYAN lawmakers investigating alleged security failings during the deadly assault on Nairobi's Westgate mall by Islamist gunmen were due to meet Tuesday, as leaders gathered to commemorate the 67 killed.

Politicians from parliament's national security and defence and foreign relations committees visited the mall on Monday afternoon, picking their way through shattered glass and pools of congealed blood in the main hall.

The four-day bloodbath at the upmarket shopping mall was brought to an end by Kenyan forces last Tuesday.

Stores had been looted completely, shopkeepers said.

Dalmas Otieno, a member of the national security committee, said lawmakers would meet Tuesday to “set up a programme” for the investigations, which are expected to last for at least several weeks.

Leaders met at inter-faith prayers attended by President Uhuru Kenyatta and led by leaders from the Muslim, Christian and Hindu communities.

Former Prime Minster Raila Odinga, speaking at the memorial, warned the attack “shows we are in for a long drawn out battle”, and stressing the need to bolster security.

“Intelligence action not acted on serves no purpose,” Odinga said.

The Red Cross on Monday said the number of people still unaccounted for stood at 39, while Kenyan and foreign investigators continued to comb the carcass of the mall for clues on the perpetrators of the raid and ensuing siege.

Part of the rooftop parking of the mall collapsed after heavy explosions and a fierce fire, leaving the key area where the insurgents are understood to have made their final stand — along with possible hostages — buried under tonnes of concrete slabs and rubble.

Shopkeepers allowed back into the mall to check on their premises painted an apocalyptic scene, saying it stank of corpses and that the first floor of the mall was completely burned.

“There's a really bad stench in there of the dead bodies and blood all over the place, that's why they're advising us to wear masks as we go in,” Pardeep Rehal, a bookstore owner, told AFP.

“You can't see anything inside any more. There is no electricity and everything is covered in ash,” another shopkeeper said.

Many shopkeepers accused the Kenyan military of looting their stores.

“There is not one shop window that is still intact, everything has been looted. My laptop has gone,” the shopkeeper added.

A beauty salon employee said that shopkeepers had locked their premises when they were evacuated, but that since then virtually all shops had been looted.

“Cash boxes have gone, jewelry has gone and handbags are missing. I was unable to find mine,” she said.

“My stock is not there,” said Angie Meseguer, who owns a boutique inside the mall.

Meanwhile rights groups condemned comments by the lawmakers that they would also “rethink” Kenya's hosting of some half a million Somali refugees, accusing the camps —notably the word's biggest such site, Dadaab — of being a “training ground” for Somali extremists. Somali refugees in Kenya, many of whom themselves fled the Shebab, have expressed fears they will be targeted in reprisal raids.

“While protecting Kenyans from security threats is an urgent priority, Human Rights Watch is concerned about reports that some members of parliament have called for the closure of the Somali refugee camps in Kenya,” said HRW's Gerry Simpson.

“These camps are currently home to over 400,000 refugees, including many forced to flee to Kenya because of Al-Shebab abuses. Forcing them back to a country still wracked by widespread violence and insecurity would not only breach Kenya's obligations under international law, but could inflame further instability in Somalia.” It is expected the lawmakers will start their meeting after the end of prayers.

“At times of problems we have to pray together at least to console one another,” Mustafa Gichuri, a 50-year-old electrician and a Muslim told AFP.

Rupy Chana, a 37-year-old Sikh woman attending the prayers, echoed that it was “good to see” people from different faiths attending the prayers.