Two Taiwanese men suspected of planting suitcases loaded with petrol on a high-speed train and in a politician's office in Taiwan were extradited from China on Tuesday, police said.

The men, identified by their family names Hu and Chu, fled to Macau on the same flight after the incidents on Friday and were nabbed in the southeastern Chinese city of Zhuhai early Sunday, said Taiwan's Criminal Investigation Bureau.

"We are treating this as a major criminal case. We have not solved the case yet and we will continue our investigation to meet the demands ... to solve it soon," police chief Wang Cho-chiun told a press conference.

Wang also thanked Chinese police for the speedy arrests and extradition of the pair, calling it a successful example of joint crime-fighting following an agreement the two sides signed in 2009.

The pair arrived in Taiwan late Tuesday afternoon and will be interrogated to clarify their motive, said Wang, adding that an initial probe have ruled out the possibility of more suspects.

Television footage showed a man with dyed blond hair wearing handcuffs and leg shackles and another man in handcuffs being escorted by the police into the bureau for questioning.

The incidents happened on Friday when two unattended suitcases were found on board a train bound for the capital Taipei, prompting the evacuation of more than 600 passengers.

Several hours later, two other suitcases also containing petrol were found in lawmaker Lu Chia-chen's office in New Taipei city where a bomb squad was called in to remove them.

Police ruled that the two cases were linked after 44-year-old Hu's DNA traces were found on the luggage at both locations while 46-year-old Chu's fingerprints were found on a van they allegedly used.

The four suitcases also contained identical contents, including gasoline, gas canisters, clocks, wires and sodium cyanide, police said.

After discovering the two suitcases on the train, rail operator Taiwan High Speed Rail Corp. evacuated passengers at Taoyuan station near Taipei and police removed the bags for investigation.

Officers searched the train for evidence and the platform for Taipei-bound trains was temporarily closed, the company said.

It said it had not received any threats prior to the incident.