Blasts rocked the Somali port city of Kismayo on Tuesday as Kenyan troops from the African Union force and their allies entered the former Islamist bastion, the force, residents and the Shebab militia said.Multiple explosions were reported in different areas of the city as troops said they had secured key strategic areas, including the harbour and airport, after a wary advance fearful of ambush by Al-Qaeda linked Shebab fighters.At least two of the blasts appeared to be African troops detonating arms caches they had unearthed, while a third, at the regional administration offices, was thought to be the work of the Shebab.In the evening a grenade hurled into a tea shop in Yasin market in the city wounded seven people, according to residents."Allied forces have fully entered and taken control of Kismayo today. All key areas including the airport, the harbour and main police stations were secured," said Somali commander Ismail Sahardid.Kismayo, a strategic seaside town of some 160,000-190,000 people, was a key base for Shebab Islamists until they abandoned their positions there Saturday.Witnesses reported at least one blast at the administration offices as Somali and AU troops moved forward into the city."It was a huge explosion," said resident Ahmed Jama, although witnesses and government officials reported no casualties.Ali Houmed, an AU force spokesman, confirmed a blast had taken place at the offices, in a part of town known as K2, and said AU troops had arrested a man suspected of planting and detonating the device.Shebab spokesman Ali Mohamud Rage said Islamist fighters were responsible and boasted of killing up to six Somali troops."We have attacked those Somali mercenaries coming into Kismayo to support the Kenyan regime," he said.The AU spokesman said there had been no casualties from the K2 blast.In addition, Kenyan army spokesman Cyrus Oguna said troops had "discovered six bombs hidden and successfully detonated them without any injuries."Ali Houmed, the AU force spokesman, said controlled blasts had taken place at the sea port but spoke of "two controlled explosions". He acknowledged there had been "a few pockets of resistance" but said troops had now taken control of the key parts of the city.A local resident, Abdi Musa, said he saw seven people wounded, one of them seriously, in the grenade attack on a tea shop.Kismayo had been the de facto capital of the Shebab for over a year, but the Islamists said they had pulled out on Saturday after Kenyan troops from the AU force launched a beach assault."We have arrested several suspected Shebab members and security operations are going on to ensure calm... we have called on all clan fighters to lay down their weapons," said Somali commander Sahardid.Kenyan forces have also pushed in by land from the west, where they have trekked in for some 200 kilometres (125 miles) after an invasion force of troops and tanks crossed the border last year, before later joining the 17,000-strong AU force.In Kismayo, the majority of residents were reported to be hiding in their homes as the troops made cautious progress, amid fears of booby traps or guerrilla attacks."Kenyan troops and Somali soldiers have reached the port... they came on foot and in lorries," said Kismayo resident Abdusalam Ibrahim."They came past, walking slowly," said resident Awil Hamad, who also confirmed the troops had taken the strategic port, as well as securing the city's old airport.AFP