Kenya's security forces have stepped up their search on the border region with Somalia for the kidnappers who killed a Kenyan national and seized four foreign aid workers from the outskirts of Dadaab, the world's largest refugee camp.
"The search is intensifying and more security forces have been sent to make every effort possible but, so far, no one has been recovered," Cyrus Oguna, the Kenyan army spokesman, told the AFP news agency on Saturday.
Despite fears the gunmen and their hostages would head for Somalia - some 100 km from Dadaab - Oguna said that he was still hopeful they remained inside Kenya.
"We had just left the camp and we were just going out towards the ... main road towards Dadaab city, and that is where we were attacked. So we were actually attacked in what is recognised as the safe part of the camp"
- Elisabeth Rasmusson, Aid worker
"We are thinking that they are in Kenya, we are making every effort that we can, and we are hopeful of a positive outcome," he added.
A Kenyan driver was killed and two others were wounded during Friday's attack on the Norwegian Refugee Council (NRC) aid convoy travelling through the refugee camp.
Kenya police said that the four foreign aid workers are a Canadian, a Filipino, a Norwegian and a Pakistani.
Aerial searches were ongoing while vehicles and troops on foot searched the remote scrubland on either side of the porous border with Somalia.
Al Jazeera's Nazanine Moshiri, reporting from Nairobi, said details remained sketchy.
"We understand that this was a high-level delegation that was touring the camp on its outskirts when they came under an organised ambush of about a dozen Somali armed men. One vehicle got away and they other was taken and driven toward the Somalia border some 80 miles away," our correspondent said.
"The vehicle was abandoned and it is unclear if the abducted workers were put in another vehicle and their whereabouts are still unknown", she added.
Elisabeth Rasmusson, secretary-general of the NRC, was travelling in the convoy when it was attacked.
"We had just left the camp and we were just going out towards the ... main road towards Dadaab city, and that is where we were attacked. So we were actually attacked in what is recognised as the safe part of the camp," Rasmusson said.
"We were attacked by, I think it was four people and they were armed, and they were armed with pistols as far as I could see, they were shooting and what happened is that they managed to take one car and we know now, what we know is that four of our expatriate colleagues are not accounted for," she said.
"The information we have is that the attackers came from the camp, and it raises serious questions that if they were refugees, how they got into the camp armed," Kenyan Defence Minister Yusuf Haji said.
Kenya has voiced concerns that Dadaab poses a security threat, and has blocked registration of new refugees at the camp.
Kenya deployed troops into Somalia last October, so even if the kidnappers succeed in crossing back into Somalia, they may have to contend with Kenyan troops on the other side of the border.
A spate of kidnapping attacks carried out by Somali gunmen last year were one of the reasons Kenya used to publicly justify its military push into Somalia.
Last October, gunmen entered Dadaab and snatched two Spanish women working for Doctors Without Borders. The two are still being held, likely in Somalia. Gunmen also carried out kidnapping attacks around the coastal resort town of Lamu.
Despite the presence of Kenyan military troops, al-Shabab rebels still control wide swaths of southern Somalia, and if the kidnappers make it into that region the hostages could be in for a long ordeal.
No claim of responsibility was immediately made after Friday's attack.