BUJUMBURA, Burundi (AFP) - Burundian President Pierre Nkurunziza arrived back in the country on Thursday, a day after a coup was declared while he was in Tanzania for regional talks, his office said.

"President Pierre Nkurunziza is now in Burundi," his senior communications advisor Willy Nyamitwe told AFP.

"That's all we can say for the now because of security reasons."

Burundian troops loyal to the President fought off soldiers backing a top general on Thursday, a day after he launched the coup in the central African nation.

Rival factions fought intense battles around the state television and radio complex, with broadcasts to the nation halted for some time, but resuming after a fierce attack by coup troops was repulsed.

The crisis has raised fears of a return to widespread violence in the impoverished country, which is still recovering from a 13-year civil war that ended in 2006 and left hundreds of thousands dead.

The coup attempt has triggered international condemnation and the United States insisted Nkurunziza remained the legitimate President.

"There are competing claims to authority, but we recognise President Nkurunziza as the legitimate President," State Department spokesman Jeff Rathke told reporters.

The UN Security Council, in emergency talks on the crisis on Thursday, condemned the coup attempt and called for a swift return to the rule of law in the impoverished country.

UN envoy Said Djinnit briefed the council, saying it was "still unclear" whether the coup attempt would succeed, a diplomat told AFP.

Nkurunziza was in neighbouring Tanzania when the coup was launched and is believed to remain in Dar es Salaam, according to Tanzanian sources, but he has not been seen since fighting began.

AFP reporters said the crackle of automatic weapons fire and the thump of explosions could be heard throughout the night Wednesday, and intensified around dawn on Thursday.

In the afternoon, after state radio broadcast a message from Nkurunziza, a major attack was launched by pro-coup troops, which was fought off, with station director Jerome Nzokirantevye saying it was "loyalist soldiers who are in control."

For much of the day the streets were largely deserted by civilians as sporadic clashes could be heard in other parts of the city, while plumes of smoke were seen on the city skyline.

The bodies of three soldiers were seen by an AFP journalist lying in the street.

Both sides claimed to control the streets.

Burundi's armed forces chief, a supporter of the President, had used national radio to declare that the coup, launched by former intelligence chief Godefroid Niyombare, had failed.

Supporters of the President also carried out attacks against independent media broadcasters in the capital, with the influential African Public Radio station ablaze after being hit by a rocket.

DIVINE BACKING

The attempted coup capped weeks of deadly civil unrest sparked by the President's controversial bid to stand for a third term.

Opposition and rights groups insist that it is unconstitutional for Nkurunziza, who has been in office since 2005, to run for more than two terms. The President, however, argues his first term did not count as he was elected by parliament, not directly by the people.

Nkurunziza, a former rebel leader from the Hutu majority and born-again Christian, also believes he ascended to the presidency with divine backing.

More than 25 people have been killed and scores wounded since late April, when Burundi's ruling CNDD-FDD party - which has been accused of intimidating the opposition and arming its own militia - nominated Nkurunziza to stand for re-election in June 26 polls.

It remains unclear, however, how many have died since the launch of the coup.

Resident Onasphore Ndayishimiye was one of the few who dared venture out on Thursday, but said he had narrowly avoided being shot.

"The police saw me and shot at me. I put my hands up and dived on the ground," said Ndayishimiye, who was unharmed but shaken.

More than 50,000 Burundians have fled the violence to neighbouring nations in recent weeks, with the UN preparing for thousands more refugees.

INTERNATIONAL ALARM

Nkurunziza's official whereabouts are unknown, after his attempt to return home was blocked by his opponents who seized the airport and ordered the borders to be shut.

However, a senior Tanzanian presidential security official told AFP Nkurunziza was still in the country.

US State Department spokesman Rathke confirmed the Burundian leader had remained overnight in Tanzania but said Washington did not know his precise whereabouts.

An AFP correspondent said the airport in the Burundian capital had been in the hands of pro-coup forces, although there were conflicting claims over who controlled it on Thursday.

The African Union Thursday condemned the violence, calling all "parties to peacefully resolve the crisis."

Those calls were echoed by Washington and the European Union which warned it was "essential the situation does not spin out of control".

In his message announcing the coup, Niyombare signalled he did not want to take power himself, vowing to form a "committee for the restoration of national harmony" and work for "the resumption of the electoral process in a peaceful and fair environment."

Niyombare is a highly respected figure who was sacked from his intelligence post in February after he opposed Nkurunziza's attempt to prolong his 10-year rule.

Asked to decide on the issue of a third term, Burundi's constitutional court found in the President's favour, but not before one of the judges fled the country, claiming its members were subject to death threats.