Islamist fighters in the Somali port of Kismayo opened fire on Monday (September 25) on residents who were burning tyres, throwing stones and chanting to protest against the Islamist takeover of the city hours earlier. A 13-year-old boy was shot dead while protesting, and two other people were injured as violence raged for several hours in Somalia's third biggest city, witnesses said. Riding in trucks with machine guns, the Islamists guarded main streets and forbade gatherings after the protests eased. The Mogadishu-based Islamists poured into Kismayo overnight to extend their grip on south-central Somalia and effectively flank the powerless central government on three sides. Ministers accused the Islamists of mounting the offensive with fighters from Eritrea, Pakistan and Yemen. One Islamist official, who spoke to a crowd in Kismayo before the protests began, said the movement was receiving help from abroad, but did not specify. "They (TFG) called foreigners, the hypocrites (TFG) called foreign hypocrites, and we are getting help from our Muslim brothers, the Islamic brothers train us, if you want to tell Bush then tell him. I know some of you are spying for them... Somalis are terrorists because foreign countries know Islam as terrorist, they want us to go against the religion," said Sheikh Hassan Turki during the protest and referring to the government's call for foreign peacekeepers. Further inflaming the situation, witnesses said more troops from the Islamists' arch-enemy -- Ethiopia -- were heading to the government's provincial base in Baidoa to bolster President Abdullahi Yusuf. Residents in the town of Berdale, about 60 kms (38 miles) from Baidoa, said they saw about 400 Ethiopian soldiers. The warlord in charge of the region fled late on Sunday. Colonel Abdikadir Adan Shire, also known as Barre Hiraale, is defence minister in Somalia's weak interim government and led the Juba Valley Alliance (JVA), an independent authority that has controlled the region around Kismayo. JVA authorities put up no resistance to the Islamists, some immediately promising to work with them. The Islamists' advances since June have challenged the aspirations of President Abdullahi Yusuf's interim government, the 14th attempt at effective central rule since warlords ousted a dictator in 1991. Analysts fear that if the Islamist-government standoff deteriorates into conflict, it could spark a major regional war in the Horn of Africa. The government denounced the Kismayo takeover as a breach of an agreement reached during peace talks in Sudan to halt military expansion and Prime Minister Ali Mohamed Gedi said he was pessimistic about further negotiations. "The attack by Islamic courts in Kismayo was an aggression to that town, it is a violation of memorandum of understanding reached so far in Khartoum, between the government and Islamic courts. Two, everybody was following and it became very evident that the Islamic courts imported illegal weapons, munitions, explosives and foreign troops into the soil of Somalia," Somalia's Prime Minister Ali Mohamed Gedi said. The Western-backed government, which is based in the provincial town of Baidoa, denounced the Kismayo takeover as a breach of an agreement reached during peace talks in Sudan to halt further military expansion. "We were committed and we are still committed, but fighting from one hand and negotiation on the other cannot work together. Already they have broken the agreement, the ceasefire, killing the people of Somalia, displacing them, so I don't see any positive approach to continue dialogue with those who are killing the people of Somalia," Gedi added at a news conference in Kenya's capital Nairobi. The Islamists and government were next due to meet in Khartoum at the end of October, but it is unclear whether that round will now go ahead. Gedi appealed to the international community to help Somalia against what he called dangerous radicals among the Islamists. Kismayo residents, near Kenya's border, said some arriving Islamist fighters had stirred up an already tense mood by burning the Somali flag and raising an Islamic one, after taking the city hours earlier without firing a shot. A Reuters witness saw thousands of men and women shout "We don't want the Islamic courts" and toss stones at trucks.