Somalia's al-Qaida-linked militant group on Saturday claimed responsibility for an explosion that killed the country's interior minister, and said they did so because the minister was "an obstacle" to its endeavor to topple the struggling government.

Al-Shabab spokesman Sheik Ali Mohamud Rage said at a press conference in the capital, Mogadishu, that militants would continue their attacks against top officials until they defeat the government of the Horn of Africa nation. Somalia has not had an effective government for two decades.

Interior Minister Abdishakur Sheik Hassan was killed Friday in an explosion in his home, and a female relative was suspected of being the bomber.

The attack followed a Thursday threat from al-Shabab that it would carry out "brazen attacks deep inside enemy territory," a reference to government-controlled areas of the capital.

Rage did not explicitly say whether the woman, whose body was found on the scene, was behind the attack, but said blame should not fall on women and children. He thanked insiders who he said helped the attack. He did not elaborate.

Hassan's official burial was expected to take place Saturday in the capital, Mogadishu.

Government forces and African Union peacekeepers in the capital on Saturday said they are beefing up security measures to prevent further attacks.

Ministry of Information spokesman Abdifatah Abdinur said security agents are "alert more than they used to be," and that "people are going through extra screening.

"If they used to be screened once in the past, today they are being frisked twice," he said.

Maj. Paddy Ankunda, spokesman for the African Union peacekeepers backing Somalia's fragile government, also said the force is on high alert.

"We know that they're planning to conduct more attacks," he said of al-Shabab militants, urging the public to be extra vigilant. "Our forces are on high alert for any possible suicide attacks."

Violent protests against an agreement calling for the ouster of the country's popular prime minister left at least two people dead on Friday.

For a country that has been swept by war and anarchy for two decades, Friday was a particularly bloody day and came barely two days after President Sheik Sharif Sheik Ahmed and the speaker of parliament signed an internationally mediated agreement extending the government's term by a year. It postponed an August presidential election until 2012 to give leaders more time to deal with security and political issues.

The government once controlled only a couple square miles (kilometers) near Mogadishu's seaside airport. African Union officials who have thousands of troops in the country shoring up the government say they now control half the city after they launched a major offensive at the beginning of the year.

But the militants appear to be fighting back after they lost key positions in the capital, and also after they suffered setbacks in other parts of the country.

Al-Shabab uses suicide bombers to demoralize the government and their African backers.

In 2009, the militants killed National Security Minister Omar Hashi Aden at a time he was preparing a multi-pronged offensive to drive them out of major towns in the country.

And several months later, the militants carried out suicide attacks on African Union base in the capital, killing more than 20 people, including 17 peacekeepers.