Scores of Ethiopian military vehicles pushed at least 80 km (50 miles) into neighbouring Somalia on Saturday, residents said, five weeks after Kenya entered Somalia to fight Islamist militants it blames for a wave of kidnappings on its soil.

The Ethiopian troops, which are in convoys of armoured vehicles, come to us today, crossing from Balanbale district on the border, Gabobe Adan, an elder in the central town of Guriel told Reuters.

They were in about 28 trucks and armed battle wagons - the armed vehicles are very big.

Other residents told Reuters that the Ethiopians had set up a base in Guriel and moved troops to other towns nearby.

Residents and officials in northeast Kenya later told Reuters that Ethiopian troops had also crossed through their towns and taken up positions near bases from where the Kenyan military is launching its offensive.

We have seen Ethiopian troops. They are clearly known to us, a local named Lesamow Said told Reuters. They arrived this evening at Damasa. Some of the soldiers crossed over to the Somalia side and started patrolling immediately.

People in the Kenyan town of Mandera, which is near both Somalia and Ethiopia, said the Ethiopians had passed through there in a convoy of 10 trucks and several armoured vehicles.

A spokesman for the Ethiopian government, Shimeles Kemal, would neither confirm nor deny the reports.

Another Ethiopian official told Reuters that an Ethiopian move to support the Kenyan assault on the al Qaeda-linked al Shabaab group was likely.

There is a strong possibility that we will be sending troops to Somalia soon to support Kenya's operation against the al Shabaab extremists, the official said, speaking on condition of anonymity.

Our deployment could either be implemented under the umbrella of AMISOM or under another form, such as a separate operation alongside Kenya, he said.

FINAL ASSAULT ON AL SHABAAB?

AMISOM is an African Union force of Ugandan and Burundian troops that has been largely responsible for keeping al Shabaab from ousting the internationally backed government.

The intention of the Ethiopian troops was not immediately clear and one local elder who did not want to be named said that they would train Somali fighters loyal to the government.

Senior Kenyan government ministers have shuttled around the east Africa region this week and travelled to the Gulf to drum up political and financial support for a coordinated campaign to rout the rebels.

Some analysts say Ethiopia may want to take advantage of al Shabaab's withdrawal from the capital Mogadishu in August to wipe out a group it sees as a threat to its stability.

Since that pullout, the militants, who want to introduce a strict version of sharia law, have resorted to suicide attacks and guerrilla-style tactics against African Union troops.

Although Ethiopian troops regularly cross the border with Somalia, and it has admitted opening humanitarian corridors into the country that it says are for food relief, residents said the numbers and locations of the troops were unusual.

I have seen about 30 Ethiopian military vehicles myself. They have entered, another Guriel resident, Farah Hussein, told Reuters. We are very happy to see them -- it is a sign of putting an end to al Shabaab.

Other people in the area, including some Ethiopian businessmen, told Reuters that Ethiopian army officers had been meeting elders in central Somalia for weeks.

Ethiopia entered Somalia in 2006, with tacit U.S. backing, to oust another Islamist movement that had taken control of the capital Mogadishu and large swathes of the country.

Its army set up a base in Guriel during that operation.

The presence of the Ethiopian troops was hugely unpopular with Somalis, and with some analysts saying it was fanning support for new militant groups, they withdrew in early 2009.

(Writing by Barry Malone; Additional reporting by Aaron Maasho in Addis Ababa, Sahra Abdi in Nairobi and Noor Ali in Garissa)