The death toll from the ongoing unrest in Cameroon's English-speaking region has risen to 17, as the government tries to quell a separatist movement, a rights group said.

Security forces opened fire on Sunday on protesters calling for the independence of the region of about eight million people.

"In order to avoid further bloodshed, the security forces must cease unnecessary and excessive use of force, and protesters should be peaceful if they want to make their voices heard. The government should investigate these killings," Ilaria Allegrozzi, Amnesty International's Lake Chad region researcher, said in a statement on Monday.

READ MORE: Cameroon shuts down internet in English-speaking areas

Internet was blocked in the region for the third day on Tuesday - the second time in less than a year. Earlier this year, the internet was blocked for three months following similar unrest. Electricity was also cut in the area.

"The reported unlawful killing of several people in the Anglophone regions by the security forces coupled with the blocks on Facebook and WhatsApp represent an extremely worrying escalation of the government's ongoing campaign to silence any form of dissent in the West and South-West regions of Cameroon," Allegrozzi said.

Analysts have called on the United Nations and the regional bloc, ECOWAS, to intervene in the crisis.

"We have seen a government that is not responsive to the demands of the Anglophone," Hans de Marie Heungoup, Cameroon analyst at International Crisis Group, told Al Jazeera on Monday.

"There is a need to strengthen and better coordinate the response of the international community since the beginning of this crisis in October 2016. It is time for the international community to act in a very strong way to avoid irreversible deterioration of the situation on the ground," Heungoup said.

Late on Monday, the UN urged Yaounde to investigate the death of protesters and to show restraint.

"The Secretary-General takes note of the calls by the authorities for dialogue and encourages representatives of the Anglophone community to seize the opportunity in their quest for solutions to the community's grievances," Stephane Dujarric, spokesman for the UN secretary-general said.

But some Cameroonians said a government-led dialogue would not solve the unrest in the region.

"The government cannot mediate on this crisis when they are the first people responsible for this escalation. They cannot mediate on the crisis they caused," Albert Nchinda, a Cameroonian political blogger, told Al Jazeera.

READ MORE: Cameroon teachers, lawyers strike in battle for English

President Paul Biya, who has been in power for 35 years, condemned the latest unrest and called for calm.

"It is not forbidden to voice any concerns in the Republic. However, nothing great can be achieved by using verbal excesses, street violence, and defying authority," Biya wrote Sunday on his official Facebook.

Cameroon's English-speaking minority say they are being marginalised by the French-speaking majority. Dissent in the two Anglophone regions - the northwest and southwest parts of the country - has been growing over the past year, with protests taking place intermittently.