JERUSALEM (Reuters) -- Israel launched two Palestinians-only bus lines in the occupied West Bank on Monday, a step an Israeli rights group described as racist and which Israel's Transport Ministry called an improvement in service.

"Creating separate bus lines for Israeli Jews and Palestinians is a revolting plan," Jessica Montell, director of the B'Tselem rights group, said on Army Radio. "This is simply racism. Such a plan cannot be justified with claims of security needs or overcrowding."

The Israeli Transport Ministry said the two new lines would "improve public transport services for Palestinian workers entering Israel" and replace pirate buses charging them "exorbitant prices".

"The Ministry of Transport has not issued any instruction or prohibition that prevents Palestinian workers from traveling on public transport in Israel nor in Judea and Samaria," it said, referring to the West Bank.

"Furthermore, the Ministry of Transport is not authorized to prevent any passenger from using public transport services."

Rights groups, however, voiced concern that Israeli police at checkpoints in the West Bank would remove Palestinian passengers from regular bus lines and order them to use the new ones.

Police spokesman Micky Rosenfeld said all Palestinians returning to the West Bank would be searched for stolen property, describing this as a routine Israeli precaution.

He said he did not know whether and how this might affect Palestinian travel on regular buses.

Herzl Ben-Zvi, mayor of the Karnei Shomron settlement, said the new lines "answer the needs of all passengers - Palestinians and settlers" because they would relieve overcrowding on buses in the area.

Last November, Israeli police ordered Palestinian workers off a bus at the request of settlers.

Settlement mayor Ron Nachman wrote on his Facebook page last year that he was working with the Israeli army, police and transport ministry to stop Palestinians boarding buses that go to Ariel.

"All of them are working on this problem, and we hope that they will soon find a solution to the reality that is bothering our people," he said.

Ma'an staff contributed to this report