Somalia's al-Shabab threatened on Wednesday to step up militant attacks against Kenya, after Nairobi refused to pull its troops out of Somalia.
Al-Shabab claimed responsibility for last week's attack on Nairobi's Westgate shopping mall, in which at least 67 people died, with 39 more listed as missing by the Red Cross.
"We will strike Kenyans where it hurts the most, turn their cities into graveyards and rivers of blood will flow in Nairobi," the al-Shabab said in a statement.
"The Kenyan government's decision to keep its invading force in Somalia is an indication that they haven't yet learnt any valuable lessons from the Westgate attacks," the extremists added, warning that Kenya was "inviting unprecedented levels of insecurity, bloodshed and destruction".
Kenya invaded southern Somalia to attack al-Shabab bases two years ago, and later joined the 17 700-strong African Union force deployed in the country.
Kenya's President Uhuru Kenyatta on Tuesday said troops had been sent to Somalia to restore order to their anarchic neighbour, and they would not leave until the job was done.
"We will not be intimated, we will not be cowed," Kenyatta said. "We will stay there until they bring order to their nation."
'Exit Somali soil'
In turn, al-Shabab said it was "fully determined to intensify attacks inside Kenya until the last KDF [Kenya Defence Force] boots exit Somali soil", saying it had the "right to defend our land and our people from enemy aggression".
"If Kenya's political leaders are still persistent in their quest to occupy our Muslim lands and carry out heinous atrocities against our people, then let them know that Kenyans will never find peace and stability in their country."
Meanwhile, Kenya's president told Somalia on Tuesday to "put their house in order", in a sign of frustration at the festering instability in the neighbouring country after the attack on the Nairobi shopping mall.
Kenyatta said he would not be bullied into withdrawing his soldiers, who are part of an African peacekeeping force.
He also took aim at the Somali government, which a source close to the Kenyan presidency said had also recently called for Kenyan troops to leave before withdrawing the demand under pressure from regional leaders.
"If their desire is for Kenya to pull out of Somalia, my friends, all they need to do is what they should have done 20 years ago, which is put their house in order," Kenyatta told religious leaders at a multi-faith prayer meeting.
Mogadishu, in turn, has been angered by Kenya's perceived close relationship with a former Islamist warlord now in control of Somalia's southernmost region, which borders Kenya.
There was no immediate reaction from the Somali government.
But al-Shabab said in a statement that if the Kenyan government's decision was to keep its forces in Somalia, it was an indication that it hadn't yet learned "any valuable lessons" from the Westgate attack. – AFP; Reuters