One of Somalia's Islamic leaders, Sheikh Dahir Aweys, says the gunmen who shot dead two people watching a World Cup match will face Islamic justice.
A cinema owner and a young girl were killed by militia loyal to the Union of Islamic Courts (UIC), who took control of much of southern Somalia last month.
The World Cup broadcast ban is not official UIC policy, but some courts do not allow matches to be shown.
Somalia has had no effective central government since 1991.
Meanwhile, video evidence has emerged that apparently shows foreign Islamist fighters helping the UIC in its fight for control of Mogadishu and Jowhar last month.
The new rulers of Mogadishu have denied the persistent allegations by members of the interim government that it is in league with foreign militia.
Mr Aweys confirmed that the gunmen had arrived to close down the cinema in the town of Dhuusa Marreeb in central Galgadud district, where a crowd had gathered to watch the Germany-Italy World Cup semi-final on Tuesday.
Some of the football fans began to protest and the gunmen fired in the air in an attempt to disperse them.
After this the angry crowd began to throw stones at the militia, who then fired at the demonstrators.
Mr Aweys told the radio station HornAfrik that he had been talking to elders in the area and it was agreed that those responsible for killing the football fans would be dealt with by Sharia.
But he said the killings were not deliberate, HornAfrik reports.
The Islamic courts have introduced Sharia in areas under their authority.
In some places, this has included a ban on cinemas and on broadcasts of World Cup games because they have carried advertisements for alcohol.
Last week, another UIC leader, Sheikh Sharif Ahmed, denied that a World Cup ban was official policy.
Mr Aweys, who denies US accusations that he has links to al-Qaeda, has called on the interim government to impose Sharia law
But our correspondent says his colleagues have offered assurances they do not want a Taleban-style state.
Over the weekend, the UIC leadership distanced itself from remarks by Osama bin Laden in the al-Qaeda's leader's most recent audio tape praising efforts to create an Islamic state in Somalia.
Now a promotional Islamist video in Arabic depicts what appears to be foreign fighters supporting the Islamic courts in fighting last month.
The video, a copy of which has been acquired by the Associated Press news agency, is done with a hand-held camera in the same style as similar films showing fighting in Iraq from the perspective of the insurgents.
It shows fighting in Somalia and what appears to be armed Arabs training at a camp in Somalia.
But Mr Ahmed has denied this: "This is related to misconceptions and bad information... To tell you the truth that camp, it exists as a camp - but there are no foreigners."
For the first time since last month's fighting, a delegation of diplomats are in Mogadishu to try to persuade the UIC leaders to agree to the deployment of an African peacekeeping force.
The Islamists oppose the move, favoured by interim President Abdullahi Yusuf.
His government is confined to the town of Baidoa and is unable to relocate to Mogadishu, now under the courts' control.
The diplomats are from the Arab League, African Union and the East African regional organisation, Igad, which last month said it intended to send a peacekeeping force of Ugandan and Sudanese troops.
However, a Ugandan army spokesman has said no troops would be deployed until it is safe to do so.
Somalis, weary after 15 years without an effective national government, are worried about a possible new conflict between Islamist and secular forces in their country, possibly backed by Ethiopia and the US, concerned about the spread of radical Islam.