Hundreds of protesters blocked a highway in Pakistan for second day on Tuesday to protest against the arrest of two women, one of whom security officials described as a would-be suicide bomber who was planning to target Chinese citizens.

Police arrested one woman who they said planned to blow herself up near a convoy of Chinese nationals and that they had recovered explosives and detonators from her.

On Tuesday officials confirmed a second woman had also been arrested.

Arrests of women are rare in southwestern Balochistan province and the detentions have enraged supporters. The protesters said they would continue their sit-in until the women, who they said were innocent, were freed.

"It is all lies," Dost Gulzar, a political activist who is leading the protest, told Reuters.

The arrests came two weeks after a woman suicide bomber blew herself up on a university campus in the southern port city of Karachi, killing three Chinese teachers.

The woman belonged to the militant separatist group the Baloch Liberation Army (BLA), which has waged a violent secessionist insurgency in Balochistan, and has targeted Chinese interests in the region.

The sit-in is taking place in the town where the women were arrested, Hoshab, some 415 miles (670 km) south of provincial capital Quetta. The highway links Quetta with Gwadar port and was built under the China-Pakistan Economic Corridor initiative.

China, a close Pakistan ally, plans to invest over $65 billion in Pakistan under the China-Pakistan Economic Corridor - a part of Beijing's Belt and Road Initiative to seek road and sea trade routes to connect with the rest of the world.

Beijing is also developing the Gwadar deep-water port.

The local administration is negotiating with the protesters, asking them to unblock the highway as a large number of vehicles are stuck, a senior official from the Balochistan police told Reuters, requesting anonymity.

Rights activists have long accused security forces of extrajudicial abductions and killings in Balochistan. Security officials say the accusations are exaggerated and not always linked with the state.

(Writing by Syed Raza Hassan; Editing by Alison Williams)