At least 64 people have been killed in two near simultaneous bomb explosions, apparently targeting crowds watching the World Cup final, in Uganda's capital, Kampala, police have said.

One blast hit an Ethiopian restaurant in the south of the city, while the other occurred at a rugby sports club in the east of Kampala.

"We have 64 dead and 65 injured. The nationalities of all the fatalities will be released later," Judith Nabakooba, Uganda's national police spokesperson, said on Monday.

The US embassy confirmed that one US citizen was among the dead and a number of other foreigners were reported to be among the injured.

Both blasts struck at the centre of large crowds watching live coverage of Sunday's World Cup football final between Spain and the Netherlands.

"These bombs were definitely targeting World Cup crowds," Kale Kayihura, the inspector-general of Ugandan police, said.

He said he believed Somalia's al-Shabab, a group which the US says has links to al-Qaeda, could be behind the attacks.

If that proves true, it would be the first time the group, which has carried out multiple suicide attacks, inside Somalia has struck outside of the country.

Hospital overwhelmed

The attacks left scores of football fans reeling in shock.

"We were watching soccer here and then when there were three minutes to the end of the match an explosion came ... and it was so loud," Juma Seiko, who was at the Kampala Rugby Club, said.

Al Jazeera's Malcolm Webb, reporting from Kampala, said dozens of injured had been taken to local hospitals, which had been overwhelmed by the number of casualties.

"All the beds are full, staff are rushed off their feet, they're really struggling to cope," he said.

Speaking by phone to Al Jazeera, Kayihura said all the signs indicated that the bombings were a "deliberate terrorist attack by a terrorist organisation".

"This was a terrorist attack," he said. "It was a deliberate, calculated attack to inflict maximum damage."

Possible suspects, other than al-Shabab, included the Allied Democratic Forces and the Lord's Resistance Army, both groups who have fought to topple the Ugandan government, Kayihura said.

Felix Kulaije, a Ugandan army spokesman, told the Reuters news agency that investigators had found the severed head of a Somali national at the scene of one of the attacks.

"We suspect it's al-Shabab because they've been promising this for long," he said.

Al-Shabab evasive

Al Jazeera's Mohammed Adow, reporting from Kenya, said the al-Shabab spokesman had refused to confirm or deny the accusations that the group was behind the attack.

"[He] told me that they are weighing matters and are going to discuss it among the senior-most leadership of al-Shabab before making a statement," he said.

"We know them as people who have been very decisive in the past, in cases like this where they have carried out bombings."

One al-Shabab commander did, however, tell the Associated Press news agency that he was happy with the attacks.

"Uganda is one of our enemies. Whatever makes them cry, makes us happy," Sheik Yusuf Sheik Issa said.

On Friday, another al-Shabab commander, Sheik Muktar Robow, called for fighters to attack sites in Uganda and Burundi - two nations that contribute troops to the 6,000-strong African Union (AU) peacekeeping force in Mogadishu.

Reprisals feared

Hassan Isilow, a Somali analyst living in Kampala, said that Somalis in Uganda feared reprisals after the claims that al-Shabab launched the attacks.

"There is fear within the Somali community at the moment," he said. "People are in panic."

"[Somalis] own lots of businesses around the city and most of them are not working today."

The force has been deployed to prop up Somalia's UN-backed government which only controls a few square kilometres of the country.

Ramtane Lamamra, the AU Commissioner for Peace and Security, condemned the attack "in the strongest posible terms".

"The attacks prove that terrorists can hit anywhere, including Africa," he said.

Lamamra said that the body's annual meeting of heads of state would go ahead in Kampala next week.

In Washington, Barack Obama, the US president, condemned the bombings.

A spokesman quoted him as saying the attacks were "deplorable and cowardly".

Mike Hammer, spokesman for the National Security Council, said in a statement that the US was "ready to provide any assistance requested by the Ugandan government".

US officials added that they were in contact with the US embassy in Kampala and in touch with the Federal Bureau of Investigation regarding requests for assistance from Uganda's government.