Kenyan troops backed by AU forces surround port city of Kismayo, last stronghold of Somali rebel group al-Shabab.

Kenyan and Somali troops have invaded Somalia’s southern port city of Kismayo, the last bastion of al-Shabab fighters, the Kenyan military has confirmed.

Cyrus Oguna, Kenya’s military spokesman, said that troops had advanced on Kismayo, seen as a decisive battle in the struggle for Somalia.

“For now, we’re not everywhere. We’ve taken a large part of it without resistance,” he said.

Al Jazeera’s Catherine Soi, reporting from Nairobi, confirmed Kenyan forces faced “minimum resistance [but] have not yet taken the whole of Kismayo”.

Al Jazeera speaks to Somali PM on the fall of al-Shabab

There have not yet been any reports of casualties in the operation which has seen the group surrounded from three sides.

Residents said they could hear fighting near the beach, 4km outside the city.

“Now we hear shelling from the ships and the [rebels] are responding with anti-aircraft guns,” Ismail Suglow told the Reuters news agency.

“We saw seven ships early in the morning and now their firing looks like lightening and thunder. Al-Shabab have gone towards the beach. Many residents have taken their guns. The ships poured many [African Union] troops on the beach.”

Al-Shabab, which was driven out of the capital Mogadishu last August and is fighting African Union forces in other parts of the country, said there was heavy fighting going on between the two sides, but denied that soldiers had entered the city.

“They invaded the town from the seaside … This morning, we sent our fighters to push them back and they are still at that position. Kismayo is under the full control of al-Shabab”, Abdulaziz Abu Musab, al-Shabab military spokesperson, told Al Jazeera by phone.

Residents of the Jubbada Hoose province city, speaking to Al Jazeera, also denied that Kenyan and Somali troops had captured the town.

Strategic location

Al Jazeera’s Mohammed Adow described Kismayo as a very important and strategic town for the group.

Kismayo, “is the backbone of the funding of al-Shabab”; it is also the location from which the group bring in their arms and supplies, he said.

Losing Kismayo, said Adow, would be “a huge setback for” the group and would leave them with the Somali capital as the only place that can provide al-Shabab with a hideout where they will also have access to “soft targets”.

Al-Shabab has called on residents of the southern city to take up arms against the Kenyan and Somali troops.

For their part, the group has downplayed the importance of the city, Musab told Al Jazeera:”losing Kismayo won’t be any worse than some of the other towns we have lost where Kenyan flags are now flying”.

Along with forces from Uganda, Burundi and Djibouti, Kenyan troops have been battling the group, which is said to have links to al-Qaeda, as part of an African Union peacekeeping force mandated with wiping out the figthers from their strongholds.

Kenya sent its troops into Somalia last October after the fighters were blamed for a series of raids on Kenyan soil

targeting its security forces as well as Western tourists.

Somalia has made progress in the past year in battling the group, who have wanted to impose their interpretation of Sharia law across the country since taking control of large swathes of south-central Somalia from 2007.

Elsewhere in Somalia, a journalist was killed in Mogadishu on Thursday night.

The death of Ahmed Abdulahi Fanah, of the Somali SAPA news agency, is the fifth such instance this week. So far in 2012, 15 journalists have been killed in the Horn of Africa nation.