By Saud Mehsud

DERA ISMAIL KHAN, Pakistan (Reuters) - Six Pakistanis working for a Polish oil and gas surveying company have been kidnapped in northwestern Pakistan, military sources told Reuters, years after a Polish engineer from the same company was beheaded by Pakistani militants.

The six Geofizyka Krakow workers were snatched from their vehicles on Saturday afternoon on a road near the village of Drazinda, about 80km (50 miles) from the city of Dera Ismail Khan, two officials with security forces in the area said.

One of the officials, who spoke on condition of anonymity as they are not authorised to speak to media, provided Reuters with the names and national identity card numbers of the workers.

Geofizyka Krakow, a subsidiary of Poland's state-run gas firm PGNiG, could not be immediately reached for comment. On its website, the PGNiG local unit said it had gone into liquidation in August 2016.

"They were sub-contractors providing works for Geofizyka Krakow, a company which is now in liquidation. They were not Polish," a PGNiG spokesman said. He declined to give any more details.

A Polish foreign ministry spokeswoman tweeted that there were no Polish citizens in the group and that the Polish embassy in Islamabad is monitoring the situation.

No militant group has claimed responsibility for the kidnappings. In the past, militants from the hardline Islamist Pakistani Taliban group have kidnapped people in the region for ransom or to bargain for the release of prisoners.

The area where the workers were kidnapped is close to South Waziristan, part of the lawless Federally Administered Tribal Areas (FATA) bordering Afghanistan.

Geofizyka Krakow has a long history of seismic survey work in Pakistan.

In 2008, a Polish engineer working for the firm was kidnapped by the Pakistani Taliban near the northwestern city of Attock, and beheaded several months later.

Overall security in Pakistan has improved over the last few years but many of the northwestern areas bordering Afghanistan remain volatile and dangerous, especially for foreigners and those working with foreign companies.

The frontier regions, deeply conservative and hard to access due to rough terrain, have long been the sanctuary of fighters from al Qaeda, the Taliban and other militant groups.

Most of the myriad militant groups that stage attacks inside Pakistan are trying to overthrow the government to establish an Islamic theocracy and impose a stricter interpretation of the religion than is practised in much of the country.

(Additional reporting by Drazen Jorgic in Islamabad and Agnieszka Barteczko in Warsaw; Editing by Louise Ireland)