The explosions killed the two bombers and wounded a Somali soldier, but no one else was wounded or killed, said Abdi Yassin, a police officer.

Interior Minister Abdisamad Mohamud said the two bombers had fake identity cards but refused to be screened by security forces, raising the suspicion of authorities.

"They sent two bombers to the assembly venue, but our heroic forces have foiled their plans and shot the two bombers," Mohamud said.

Somali leaders - 825 of them - began a nine-day meeting on July 25 to examine, debate and vote on the constitution, a document that's been years in the making. A vote by the group, known as the National Constituent Assembly, is a key step in a flurry of political activity in Somalia over the next month.

The U.N. mandate for Somalia's current government expires on Aug. 20, and Somali leaders are to vote on the constitution, vote in a new 275-member parliament, then vote on a president all before then. If the assembly votes down the constitution, the new parliament will have to debate it and then vote on it.

Security has improved markedly in Mogadishu over the last year, leading to a general revival of the seaside capital. But al-Shabab militants still infiltrate the city and carry out suicide attacks, particularly at high-profile events. African Union and Somali forces pushed al-Shabab fighters out of Mogadishu on Aug. 6, 2011.

The country's current constitution is the Transitional Federal Charter, which was written in 2004. Meant only as a temporary charter, it contains fewer rights than are spelled out in the new draft constitution.

The draft constitution makes it clear that Islamic law is the basis for Somalia's legal foundation. No religion other than Islam can be propagated in the country and all laws must be compliant with Shariah -Islamic - law. But the draft has more progressive aspects as well: In its original draft the constitution protects the right to an abortion to save the life of the mother. It also would ban the circumcision of girls, a practice opponents call female genital mutilation.

Somalia has not had a powerful central government since 1991, when the president was killed and the country collapsed into chaos. The international community is working to create a government respected by the people that can provide goods and services in and outside the capital.