QUETTA, Pakistan (Reuters) -- Pakistani police have said they had rounded up about a dozen people for questioning in the search for a senior UN refugee agency official abducted in the city of Quetta.
American John Solecki, head of the United Nations High Commission for Refugees (UNHCR) office in the southwestern province of Baluchistan, was abducted on February 2 after gunmen ambushed his vehicle and killed his driver.
Attacks on foreign aid workers, company employees, and diplomats have increased in Pakistan over the past year, especially in areas near the border with Afghanistan, where Taliban and Al-Qaeda militants are battling government forces.
Thousands of foreign company employees, aid workers, and diplomats are based in Pakistan. Few companies or aid groups have pulled out of the country, but most organizations have restricted travel to dangerous areas.
Senior Quetta police officer Wazir Khan Nasir said about a dozen people with criminal links had been detained for questioning in the hope of uncovering clues to Solecki's abductors and his whereabouts.
"The difficulty is that no one has claimed responsibility. We can't single out the Taliban. We're investigating, we're trying our best," Nasir told Reuters.
Quetta is the capital of Baluchistan Province, which borders Afghanistan and Iran. Both Taliban and separatist Baluch militants operate in the province where the UNHCR is helping Afghan refugees.
Nasir said security forces set up checkpoints on routes out of the city soon after the kidnapping and they had been searching vehicles but found nothing. That raised the possibility the kidnappers still had Solecki in Quetta, he said.
Security has also been stepped up at crossing points on the Afghan border to stop the kidnappers taking Solecki there.
UN Secretary-General Ban Ki-moon condemned Solecki's abduction and the killing of his driver and called for Solecki's immediate release.
Two Chinese telecommunications engineers, a Polish oil company engineer, two Afghan diplomats and an Iranian diplomat were kidnapped in the northwest last year. Pakistani Taliban militants were responsible for at least some of the abductions.
One of the Chinese engineers escaped from his Taliban captors, but the other five victims are still being held.
Gunmen shot dead an American aid official and his driver outside the American's home in the northwestern city of Peshawar in November. An American diplomat escaped unhurt when gunmen ambushed her vehicle in Peshawar in August.
The Polish engineer's company said it was ceasing its Pakistani operations after the man was abducted.
The United Nations ordered the children of foreign staff to leave in October after a suicide bomb attack on the Marriott Hotel in Islamabad killed 56 people, including six foreigners.