Bronislaw Komorowski took the oath of office as Poland's new president today and vowed to build national unity, but the man he beat for the top job boycotted the ceremony in a sign of enduring political tension.
Mr Komorowski, a moderate conservative from the ruling Civic Platform (PO), defeated Jaroslaw Kaczynski in the July 4th runoff of an election triggered by the death of Mr Kaczynski's twin brother, president Lech Kaczynski, in a plane crash in April.
"Poland needs cooperation between the most important institutions of the state, between the government, the parliament, the president but also between political parties, between those in government and those in opposition," Mr Komorowski said in a speech to parliament after taking the oath.
"As president I declare my will for such cooperation."
Relations between Lech Kaczynski, a combative right-winger, and prime minister Donald Tusk's centrist, pro-business government were often difficult, with the president using his power of veto to block some legislation.
Jaroslaw Kaczynski, who leads the right-wing main opposition Law and Justice party (PiS), and some of his deputies stayed away from the ceremony.
Asked why Mr Kaczynski did not attend, the deputy head of the PiS parliamentary party, Beata Szydlo, told Reuters: "It is his individual decision. Clearly he has some other things to do."
The moustachioed, gently-spoken Komorowski, a Tusk ally, is expected to work much more smoothly with the government as it tries to tackle Poland's growing debt pile and large budget deficit without derailing a still-fragile economic recovery.
In his speech, Mr Komorowski paid tribute to the 96 people who died in the April 10th plane crash in Russia. But he said Polish democracy had proven its resilience in quickly overcoming the tragedy, which claimed the lives of many top officials along with Mr Kaczynski and his wife.
Mr Komorowski also stressed Poland's commitment to the European Union, which it joined in 2004, and said his first overseas trips as president would be to Brussels, Paris and Berlin.
Supporters of the Kaczynski twins earlier this week blocked an attempt by the authorities to move a large wooden cross from in front of the presidential palace to a nearby church.
The cross was erected shortly after the crash and has become a de facto shrine commemorating those who died. The noisy protests that prevented its removal underscored the continued strong emotions still felt by some Poles about the tragedy.
Mr Kaczynski's no-show at today's ceremony drew criticism from Jerzy Buzek, a former centre-right prime minister who heads the European Parliament.
"There are certain events in a democratic state when all should be present and when their absence is regarded as a deliberate protest," Mr Buzek said.
Other guests at the swearing-in ceremony included ex-presidents Lech Walesa and Aleksander Kwasniewski and former activists of the pro-democracy Solidarity trade union that toppled communism in 1989.
Mr Komorowski (58) is Poland's fourth post-communist president. A historian by training, he was born in communist Poland into a family with aristocratic roots. He and his wife Anna have five grown-up children.
A member of underground pro-democracy organisations under communism, he later served as defence minister in 2000-01 and became speaker of the lower house of parliament, the Sejm, in 2007 when Mr Tusk's PO won the parliamentary election.
Reuters