Pakistan has arrested a suspect in Tuesday's deadly car bombing attack in the southern city of Karachi. The attack killed three people and injured 22 others. The investigation is focusing on tribal rebels from Baluchistan, Pakistan's poorest province.

Pakistan's President Pervez Musharraf announced the arrest in a news conference Wednesday.

"The man who did it, we have arrested," he said. "But we are trying to get more: who is he representing really and what was his motivation."

The president said several other people also are being questioned but provided no additional details.

However, police say the investigation is focusing on the Baluchistan Liberation Army, a militant group that initially claimed responsibility for the bombing.

The group is demanding greater control over valuable natural gas deposits in Baluchistan province and is behind a number of small rocket attacks there.

Officials in Karachi say Tuesday's bomb was hidden in a car parked outside a building housing the offices of the state-run oil company, Pakistan Petroleum and a fast-food restaurant on the ground floor.

The blast gutted the KFC restaurant and destroyed several nearby cars.

The attack has also sparked security concerns across the country as the government prepares for some high-profile international events.

Later this week, delegates from around the world, including U.N. Secretary-General Kofi Annan, will meet in the capital to discuss funding for earthquake relief operations.

President Musharraf is seeking $5.2 billion from international donors.

And in a few weeks the English cricket team is scheduled to visit Karachi where it will play a one-day test match against Pakistan's national team.