By Muhammad Hashim

KOHAT, Pakistan (Reuters) - At least 16 people were killed and 50 wounded in a car bomb attack at a police residential complex in Pakistan on Tuesday, officials said, in another blow for a country grappling with devastating floods.

The blast in the northwestern garrison town of Kohat came hours after Taliban threatened more suicide attacks on a government and security forces already overwhelmed by the worst floods in Pakistan's history.

"Many houses collapsed due to the blast. People are trying to dig them out," a Reuters reporter at the scene said.

Police official Dilawar Khan Bangash said explosives were planted in a car parked near the gates of the complex but he was not sure whether they were detonated via remote control or by a suicide bomber.

Islamist militants have killed nearly 120 people in suicide bombings since resuming a bloody campaign last week to topple the government after a one-month lull during Pakistan's floods.

A Taliban spokesman on Tuesday threatened more suicide attacks on security forces and government offices in response to U.S. drone aircraft strikes on its members in tribal areas.

"Americans are carrying out drone attacks with the permission of Pakistan and we will take revenge with suicide attacks on security forces, police and government offices," Taliban spokesman Azim Tariq told Reuters by telephone from an undisclosed location.

"Drone attacks have killed dozens of innocent women and children but America has never expressed its regret."

Nineteen people, including policemen and children, were killed in a suicide bombing at a police station in the northwestern town of Lakki Marwat on Monday.

Renewed violence and the floods, which killed more than 1,700 people and made millions homeless, have raised questions about the stability of nuclear-armed Pakistan, which Washington sees as a vital ally in the U.S. war against militancy.

GLOBAL HUB FOR MILITANTS

In the past week, drone attacks killed at least 21 suspected militants in the Waziristan region, near the Afghan border and described as a global hub for militants.

The U.S. has stepped up drone missile strikes in Pakistan's northwestern tribal belt since a Jordanian suicide bomber killed seven CIA employees at a U.S. base in Afghanistan in December.

Last week, U.S. prosecutors charged Hakimullah Mehsud, the leader of the Pakistani Taliban who appeared in a farewell video with the Jordanian, in the plot to kill the CIA agents.

Containing the Taliban will be especially difficult now for the government, which has been widely criticized for its slow response to the floods and is under growing pressure to help rebuild and provide millions of flood victims with compensation.

Pakistan's government is also battling with the perception that any aid money it handles will not reach flood victims.

According to the U.N., only 22 percent of aid coming to Pakistan is channeled to the government, with the rest administered by the world body, the Red Cross and Red Crescent Movement, and international and Pakistani NGOs.

"People need cash right away to rebuild their homes and their means of making a living," Ajay Chhibber, the UNDP's director for Asia and Pacific, told a news conference in Islamabad.

"Credible oversight and monitoring mechanisms in the country will help to attract more funding resources for the monumental task ahead in all of the flood-affected area."

(Additional reporting by Zeeshan Haider; Writing by Augustine Anthony; Editing by Chris Allbritton and Michael Roddy)