Strong aftershocks and a tsunami alert rocked Chile and rattled nerves as rightwing billionaire Sebastian Pinera was sworn in as the new president of the quake-hit nation.

"We're going to rebuild Chile together, stone by stone, brick by brick," Pinera pledged in his first speech as president only hours after his inauguration and a 6.9-magnitude aftershock that sent people scrambling for higher ground.

"In some way, we are all survivors of this tragedy," Pinera said.

The tremors, the strongest since February's 8.8-magnitude quake, triggered the alert which lasted four hours on parts of the mainland and caused panic at the parliament in the coastal city of Valparaiso where Pinera was inaugurated.

Many guests, including seven Latin American heads of state, were visibly shaken, and the parliament was urgently evacuated straight after the ceremony.

The aftershocks in central areas peaked at a magnitude of 6.9, the strongest in a wave of more than 250 which have shaken Chile since the February 27 quake, which sparked a killer tsunami and left almost 500 confirmed dead and some two million people affected by the disaster.

No damage or injured were reported Thursday, but authorities, who had been criticized for their slow response after the first quake, issued a tsunami alert which was later lifted on land but maintained for Easter Island.

Pinera, 60, inherited the presidency from widely-popular leftwing leader Michelle Bachelet and faces the huge challenge of rebuilding the nation.

On his return to Santiago, the business tycoon called on all Chileans to pull together to rebuild their nation.

"To get there, we need to have unity not divisiveness, generosity not selfishness... we're going to have to dry our tears and roll up our sleeves," he said from a balcony of the La Moneda presidential palace, surrounded by his wife and four children.

"Despite the suffering and adversity, we must have the courage and will to dry our tears and get to work to confront the emergency and start reconstruction," he said.

His earlier visit was to the ravaged coastal town of Constitucion, where he offered 80-dollar vouchers to children of poor families to help ease post-quake recovery.

Pinera said the vouchers would benefit some 4.2 million children, and that he would propose a law to congress on Friday to back the measure, which he hoped would be applied by early April.

Joined by several ministers, he also placed a floral tribute at a spot where huge waves swept up from the sea on February 27.

His January victory spelled an end to the ruling left-wing coalition that has governed Chile since the end of General Augusto Pinochet's dictatorship 20 years ago.

But the presidency of Pinera, who placed 437th Wednesday on the latest Forbes list of the world's wealthiest people with a net worth of 2.2 billion dollars, will be marked by the aftermath of the quakes.

Analysts estimate reconstruction could cost up to 15 billion dollars.

The Inter-American Development Bank (IDB) made available 460 million dollars in loans for Chile's reconstruction efforts, bank officials said Thursday.

Crowds waved as they bid goodbye to Bachelet, known to some as the "mother" of Chileans, at the La Moneda Palace in Santiago.

Satirical newspaper The Clinic headlined its backpage with the title, "Don't go, mum," while banners called for the nation's first female leader to stand for president again in 2014 elections.

Pinera, a self-proclaimed centrist, has promised he will build on the policies practiced by his predecessor, rather than replace them.

After vowing austerity during his campaign, he is now expected to ramp up spending, borrow abroad and dip into savings from export revenues from the key copper mining industry.

During his campaign, Pinera deflected accusations of potential conflicts of interest between his political ambitions and his corporate empire, which includes shares in Chile's national airline, LAN, which he vowed to sell by inauguration day, and also in a football team, music company and TV channel.

He also successfully put a distance between himself and Pinochet's dictatorship, which had enjoyed the backing of several right-wing parties now behind the billionaire.

Chile's economy shrank two percent last year, its first contraction in a decade, and it was forecast before the quake to grow between 4.5 and 5.5 percent in 2010.