Suicide bombs remain a constant threat in Somalia

The conference will focus on rebuilding its security forces and tackling rape - a largely taboo subject in Somalia.

Somalia is widely regarded as a failed state, hit by an Islamist insurgency, piracy and a famine from 2010 to 2012.

At least seven people were killed in a car bomb attack in the capital, Mogadishu, on Sunday.

Al-Shabab, which is part of al-Qaeda, said it carried out the attack.

Tuesday's meeting - which Mr Cameron will co-host with Somalia's President Hassan Sheikh Mohamud - follows similar conferences in London and the Turkish city of Istanbul last year, amid growing international concern that Somalia has turned into a haven for al-Qaeda-linked militants.

"I hope we can all get behind a long-term security plan - one that ends the Shabab's reign of terror forever," Mr Cameron said.

"I also hope we can improve transparency and accountability so people know where resources are going. We also need to continue the process of rebuilding the Somali state, with all the regions of Somalia around the table and the neighbouring countries too."

BBC Somalia analyst Mary Harper says there has been a dramatic change in the country in the past year.

There is a new government - the first one in more than two decades to be recognised by the United States, the International Monetary Fund (IMF) and other key players, she says.

Al-Shabab has lost control of the major towns, pirate attacks off the Somali coast have fallen dramatically and the famine, which the United Nations estimates claimed nearly 260,000 lives, is over, she adds.

However, massive challenges remain, as al-Shabab still has the capacity to carry out attacks and the government depends on about 18,000 African Union (AU) troops for its security, our correspondent says.

Somalia is also divided into a patchwork of self-governing regions, many of them hostile to the central government.

The breakaway state of Somaliland and the semi-autonomous region of Puntland say they will boycott the conference.

The conference will address an issue that was until recently completely taboo in Somalia - rape, especially of women living in camps for displaced people, our correspondent says.

Somali aid worker Halima Ali Adan told the BBC the decision to tackle the issue at the conference was a big step forward.

"Sexual violence is something that was not ever spoken about in Somalia," she said.

"The international community themselves have seen the importance of this issue to be addressed as soon as possible because it is actually overwhelming."

Delegates from more than 50 countries and organisations are expected to attend the meeting.

On Monday, Qatar said Sunday's suicide attack in Mogadishu had targeted its officials, Qatar's official QNA news agency reported.

The four officials were travelling in armoured vehicles belonging to the Somali government when the convoy was attacked, it said.

None of the Qatari nationals were injured, QNA reported.

However, 10 other people were wounded in the attack, according to a BBC correspondent in Mogadishu.

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