Peru"s election front-runner Pedro Castillo called on his supporters to "stay alert" on Friday as legal wrangles over the ultra-close vote count ignited tensions in the Andean nation with his socialist party seemingly poised for victory. Castillo, an elementary school teacher who has fired up support from poorer, rural Peruvians, raised concerns about plans by the opposition to nullify votes and sought clarity from the electoral body over the process. "We call on the Peruvian people to stay alert," he said. The comments underscored rising tensions in the copper-rich nation that has been on tenterhooks since the Sunday vote. Castillo has 50.2% of the ballots, narrowly ahead of right-wing Keiko Fujimori, who has made unsubstantiated allegations of fraud. Vladimir Cerron, the Marxist-Leninist head of Castillo"s Free Peru party, was even more strident, saying on Twitter that "the people must rise up" in defense of the vote. He had earlier claimed victory for Castillo in the knife-edge election. With close to 99.6% of votes tallied and only a handful of contested ballots to be added, Castillo was some 60,000 votes ahead of Fujimori. The country"s electoral authority has yet to confirm the win, but most observers and some regional leftist leaders including from Argentina and Bolivia have proclaimed Castillo as the victor, prompting protests from Peru"s government. "Several presidents in the world are congratulating the victory of Pedro Castillo, in other words, he has solid international legitimacy," Cerron wrote. RADICAL INFLUENCE Cerron, a Cuba-trained surgeon and Marxist-Leninist, is a former regional governor who could not run for president himself as he has been sentenced on corruption grounds in the past and is seen as a more radical potential influence on Castillo. Fujimori has yet to concede the election with fewer than 100,000 votes remaining to be counted and her supporters have called for protests against the result. The daughter of jailed former President Alberto Fujimori, she has doubled down on unsubstantiated allegations of fraud, and members of her party have said they will not concede until all votes and appeals are counted, which could still take days. Castillo himself has also stopped short of proclaiming himself the winner, although he did say earlier this week that the party had assured him he would be the winner. The election has bitterly divided Peruvians, with higher-income citizens supporting Fujimori while low-income ones supported Castillo, including in key mining regions of the country, the world"s no. 2 copper producer. read more Castillo was not a member of the Free Peru party before his presidency run. It is still unclear whether he would adopt a far-leftist stance for the economy if in power. In recent days, he has recruited Pedro Francke, a moderate left economist as his adviser, who has looked to foster a more market-friendly tone.