* PM Abiy's forces captured Tigrayan capital Mekelle
* TPLF says it is still fighting near Mekelle
* Some fear protracted guerrilla war in northern region
* Nearly month-long war has destabilised east Africa
ADDIS ABABA/NAIROBI, Nov 30 (Reuters) - Ethiopia's Prime Minister Abiy Ahmed lauded his troops on Monday for ousting a rebellious northern movement, but the leader of Tigrayan forces said they were still resisting amid fears of a protracted guerrilla conflict.
The nearly month-long war has killed hundreds and probably thousands of people, sent refugees into Sudan, enmeshed Eritrea, and stirred rivalries among Ethiopia's myriad ethnic groups.
Federal forces captured regional capital Mekelle at the weekend and declared victory over the Tigray People's Liberation Front (TPLF), a guerrilla movement-turned-political party that dominated national government for nearly three decades until 2018.
"Our constitution was attacked but it didn't take us three years, it took us three weeks," Abiy told parliament, comparing his offensive with the American Civil War of the 1860s.
"Our army is disciplined and victorious."
Though the TPLF said Mekelle suffered bombardment, Abiy said his troops had declined to use rockets and not killed a single civilian in Tigray since starting an offensive in response to an attack on a federal army base on Nov. 4.
Though the highland city of 500,000 people eventually fell with little resistance, the TPLF said on Sunday it had shot down a plane and retaken one town.
'FIGHTING THE INVADERS'
TPLF leader Debretsion Gebremichael, a 57-year-old former radio operator, denied reports he had fled to South Sudan and said his forces captured some soldiers from neighbouring Eritrea around Wukro, about 50 km (30 miles) north of Mekelle.
"I'm close to Mekelle in Tigray fighting the invaders," he told Reuters in a text message.
Claims from all sides are difficult to verify since phone and internet links to Tigray have largely been down and access is restricted.
The TPLF has shelled Asmara's airport and accused Eritrea of sending troops to fight with Abiy's forces. Both Eritrea and Ethiopia have denied that accusation.
When he took office in 2018, Abiy pledged to unite Ethiopia's 115 million people, but ethnic bloodshed had killed hundreds and uprooted hundreds of thousands from their homes even before the latest flare-up.
In Tigray, both sides have spoken of hundreds of fatalities in air strikes and fighting. Diplomats believe the toll is in the thousands.
Abiy's spokeswoman Billene Seyoum dismissed the TPLF's comments that fighting continued, saying: "Tracking and responding to the many delusions of a disintegrating criminal clique that has become irrelevant is not our focus."
Redwan Hussein, chair of a special government taskforce on Tigray, told Reuters most casualties occurred at the beginning of the conflict during a TPLF attack on Ethiopian soldiers, attempts by reinforcements to reach them, and then a mass killing of about 700 civilians.
"Our orders were to leave the cities alone, and to encircle them, to cut the forces that were within the towns from their chain of commands," he added, saying the elite Republican Guard captured Mekelle without shooting as TPLF conscripts deserted.
The TPLF was not immediately available to comment. On Sunday, the Red Cross said Mekelle's hospitals were low on supplies and bodybags, but did not give casualty figures.
It is not clear how many fighters the TPLF has left, but Debretsion's defiance raises the spectre of a drawn-out insurgency. The battle-hardened TPLF helped topple Ethiopia's Marxist dictatorship in 1991 and knows how to exploit its mountains and borders with Sudan and Eritrea.
Abiy, whose parents are from the larger Oromo and Amharic groups, said he had felt Ethiopia's ethnic frictions even when taking office as prime minister, where he felt like a "prisoner." He said security services dominated by Tigrayans discouraged him from travelling round Ethiopia.
There are more than 80 ethnicities in Ethiopia, which operates as a federation of 10 regions run by separate groups.
Abiy said he had directed reforms to reduce Tigrayans in senior military positions from more than 60% to a quarter of the top brass. Tigrayans make up roughly 6% of the population.
Though urging the more than 45,000 refugees in Sudan to return, the prime minister said it was suspicious so many of them were young males and if any had a role in an alleged massacre of non-Tigrayans in Mai Kadra they should face justice.
The government blamed the killings on a Tigrayan youth group with the aid of local forces, but the TPLF denied any collusion.
(Reporting by Addis Ababa newsroom, and Duncan Miriri and David Lewis in Nairobi; Writing by Andrew Cawthorne; Editing by William Maclean, Jon Boyle and Angus MacSwan)
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