Two bombings in the Algerian capital, Algiers, confirm a recent trend in the North African country of spectacular attacks on new types of targets.
It is the second major bombing in Algiers in eight months
They also cast doubt on Algeria's ability to put more than a decade of bloody conflict behind it.
In recent years the level of political violence in Algeria has been steadily dropping.
Attacks blamed on Islamist extremist groups were largely limited to ambushes and skirmishes targeting the police or army in rural areas.
But this is the second time in eight months that bombers have hit in the heart of the capital, which had been spared major attacks for several years.
Pattern of violence
On 11 April suicide bombings claimed by al-Qaeda's North African wing hit the government's central offices and a police station on the outskirts of Algiers.
Tuesday's first blast hit a bus carrying students near the constitutional court in Algiers, while the second appears to have targeted the UN offices in a smart residential district near the city centre.
Foreign workers have been targeted in recent months
The attacks fit a pattern of violence that has developed since the remnants of Algeria's Islamist insurgency confirmed an allegiance with al-Qaeda in September, 2006.
There has been little evidence of operational links between Algeria's militant groups and the broader al-Qaeda network, security analysts say.
But the tactics of the Algerian militants, who now call themselves Al-Qaeda in the Islamic Maghreb, have changed.
Militants have employed slick propaganda on the internet to recruit young Algerians deployed in suicide bombings.
The security forces are still targets, but there have also been attacks against more prominent symbols of the state.
A man blew himself up in a crowd of people waiting for President Abdelaziz Bouteflika on a visit to the eastern city of Batna in September.
There have also been several attacks and threats against foreign workers in Algeria over the last year.
Last month, al-Qaeda's deputy leader Ayman al-Zawahiri made a public call for attacks to be carried out across North Africa.
Western companies have scaled back operations or decided not to send foreign workers.
The government has long described this violence as residual, saying that the attacks are the work of a shrinking band of militants desperate to make a show their force.
In recent months, the army has launched major security sweeps across the country, and security services claim to have arrested or killed some senior figures within Al-Qaeda in the Islamic Maghreb.
Security has been tight since 1992, when violence broke out after the army cancelled the second round of Algeria's first multiparty elections to prevent a victory by an Islamist group.
The country has remained under a state of emergency, with roadblocks and car searches common.
But despite these measures, attacks blamed on al-Qaeda-linked militants have continued, raising tension in a country that hoped it was well on the way to a full recovery.